Engine Mechanical (H4SO) (except Sti) Subaru Impreza WRX STI GR

SPECIFICATION

GENERAL SPECIFICATION

Note. US: Undersize OS: Oversize

GENERAL SPECIFICATION

Scheme 341

Tightening torque: N.m (kgf-m, ft-lb)

T1. 5 (0.5,3.7)

T2: 9.75 (1.0,7.2)

T3: 24.5 (2.5,18.1)

T4: 39 (4.0,28.8)

T5: 78 (8.0,57.5)

T6: Refer to INSTALLATION , Crank Pulley.

Scheme 342

Tightening torque: N.m (kgf-m, ft-lb)

T1. 6 (0.6,4A)

T2: 6.4 (0.7,4.7)

T3: 8 (0.8,5.9)

T4: 9.75 (1.0,7J2)

T5: 10 (1.0,7.4)

T6: 17 (1.7, 12.5)

T7: 18 (1.8,13.3)

T8: 25 (2.5,18.4)

T9: Refer to INSTALLATION , Cylinder Head.

T10: Refer to INSTALLATION , Valve Rocker Assembly.

Scheme 343

Tightening torque: N.m (kgf-m, ft-lb)

T1: 6 (0.6,4.4)

T2: 9.75 (1.0,7.2)

T3: 25 (2.5,18.4)

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Scheme 345

Tightening torque: N.m (kgf-m, ft-lb)

T1: 5 (0.5,3.7)

T2: 6.4 (0.7,4.7)

T3: 10 (1.0,7.4)

T4: 25 (2.5, 18.4)

T5: Refer to INSTALLATION , Cylinder Block.

T6: 16 (1.6,11.8)

T7: First 12 (1,2,8.7) Second 12 (1.2, 8.7)

T8: 44 (4.5,32.5)

T9: 45 (4.6,33.2)

T10: 70 (7.1,51.6)

Scheme 346

Tightening torque: N.m (kgf-m, ft-lb)

T1: 45 (4.6,33.2)

T2: 72 (7.3,53.1)

Scheme 347

Tightening torque: N.m (kgf-m, ft-lb)

T1: 35 (3.6,25.8)

T2: 42 (4.3,31.0)

T3: 85 (8.7,62.7)

CAUTION

1. Wear appropriate work clothing, including a cap, protective goggles and protective shoes when performing any work.
2. Remove contamination including dirt and corrosion before removal, installation or disassembly.
3. Keep the disassembled parts in order and protect them from dust and dirt.
4. Before removal, installation or disassembly, be sure to clarify the failure. Avoid unnecessary removal, installation, disassembly and replacement.
5. Vehicle components are extremely hot after driving. Be wary of receiving burns from heated parts.
6. Be sure to tighten fasteners including bolts and nuts to the specified torque.
7. Place shop jacks or rigid racks at the specified points.
8. Before disconnecting connectors of sensors or units, be sure to disconnect the ground cable from the battery.
9. All parts should be thoroughly cleaned, paying special attention to engine oil passages, pistons and bearings.
10. Rotating parts and sliding parts such as piston, bearing and gear should be coated with oil prior to assembly.
11. Be careful not to let oil, grease or coolant contact the timing belt, clutch disc and flywheel.
12. All removed parts, if to be reused, should be reinstalled in the original positions and directions.
13. Bolts, nuts and washers should be replaced with new parts as required.
14. Even if necessary inspections have been made in advance, proceed with assembly work while making rechecks.
15. Remove or install the engine in an area where chain hoists, lifting devices, etc. are available for ready use.
16. Be sure not to damage coated surfaces of body panels with tools, or not to stain seats and windows with coolant or oil. Place a cover over fender, as required, for protection.
17. Prior to starting work, prepare the following: Service tools, clean cloth, containers to catch coolant and oil, wire ropes, chain hoist, transmission jacks, etc.
18. Lift up or lower the vehicle when necessary. Make sure to support the correct positions.

SPECIAL TOOL

SPECIAL TOOL SPECIFICATION ILLUSTRATION TOOL NUMBER DESCRIPTION REMARKS 18231AA010 CAM SPROCKET WRENCH Used for removing and installing cam sprocket. (LH side) CAM SPROCKET WRENCH (499207100) can also be used. 1B022XU0 SUBARU SELECT MONITOR III KIT Used for various inspections. 498267800 CYLINDER HEAD TABLE Used for replacing valve guides. Used for removing and installing valve spring. 498277200 STOPPER SET Used for installing automatic transmission assembly to engine. 498457000 ENGINE STAND ADAPTER RH Used together with ENGINE STAND (499817100). 498457100 ENGINE STAND ADAPTER LH Used together with ENGINE STAND (499817100). 498497100 CRANKSHAFT STOPPER Used for removing and installing the flywheel and drive plate. 498747300 PISTON GUIDE Used for installing piston in cylinder. 498857100 VALVE OIL SEAL GUIDE Used for press-fitting of intake and exhaust valve guide oil seals. 499017100 PISTON PIN GUIDE Used for installing piston pin, piston and connecting rod. 499037100 CONNECTING ROD BUSHING REMOVER AND INSTALLER Used for removing and installing connecting rod bushing. 499587200 CRANKSHAFT OIL SEAL INSTALLER Used for installing crankshaft oil seal. Used together with CRANKSHAFT OIL SEAL GUIDE (499597100). 499587500 OIL SEAL INSTALLER Used for installing the camshaft oil seal. Used together with OIL SEAL GUIDE (499597000). 499587700 CAMSHAFT OIL SEAL INSTALLER Used for installing cylinder head plug. 499097700 PISTON PIN REMOVER ASSY Used for removing piston pin. 499207400 CAM SPROCKET WRENCH Used for removing and installing cam sprocket. (RH side) 499497000 TORX® PLUS Used for removing and installing camshaft cap. 499587100 OIL SEAL INSTALLER Used for installing oil pump oil seal. 499597000 OIL SEAL GUIDE Used for installing the camshaft oil seal. Used together with CAMSHAFT OIL SEAL INSTALLER (499587500). 499597100 CRANKSHAFT OIL SEAL GUIDE Used for installing crankshaft oil seal. Used together with CRANKSHAFT OIL SEAL INSTALLER (499587200). 499718000 VALVE SPRING REMOVER Used for removing and installing valve spring. 499767200 VALVE GUIDE REMOVER Used for removing valve guides. 499767400 VALVE GUIDE REAMER Used for reaming valve guides. 499767700 VALVE GUIDE ADJUSTER Used for installing valve guides. (Intake side) 499767800 VALVE GUIDE ADJUSTER Used for installing valve guides. (Exhaust side) 499817100 ENGINE STAND Stand used for engine disassembly and assembly. Used together with ENGINE STAND ADAPTER RH (498457000)&LH (498457100). 499977400 CRANK PULLEY WRENCH Used to stop rotation of the crank pulley when loosening or tightening crank pulley bolts. (AT model) 499977100 CRANK PULLEY WRENCH Used to stop rotation of the crank pulley when loosening or tightening crank pulley bolts. (MT model) 499987500 CRANKSHAFT SOCKET Used for rotating crankshaft. 42099AE000 QUICK CONNECTOR RELEASE Used for removing the quick connector. 18354AA000 VALVE ROCKER HOLDER Used for installing the valve rocker assembly (intake). (2-piece set) 18258AA000 SPRING INSTALLER Used for installing the valve rocker assembly (intake)

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GENERAL TOOL

GENERAL TOOL SPECIFICATION

PROCEDURE

It is possible to conduct the following service procedures with engine on vehicle, however, the procedures described in this information are based on the condition that the engine is removed from vehicle.

1. V-belt
2. Timing belt
3. Valve rocker assembly
4. Camshaft
5. Cylinder head

INSPECTION

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1. After warming-up the engine, turn the ignition switch to OFF.
2. Make sure that the battery is fully charged.
3. Remove the fuse of fuel pump from main fuse box.
4. Start the engine and run it until it stalls.
5. After the engine stalls, crank it for five more seconds.
6. Turn the ignition switch to OFF.
7. Remove all spark plugs. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/ignition-system/#engine-ignition-system-h4so-except-sti__removal) , Spark Plug.
8. Fully open the throttle valve.
9. Check the starter motor for satisfactory performance and operation.
10. Secure the compression gauge tightly against the spark plug hole. NOTE: When using a screw-in type compression gauge, the screw should be less than 18 mm (0.71 in) long.
11. Crank the engine by the starter motor, and read the maximum value on the gauge when the needle of compression gauge is steady.
12. Perform at least two measurements per cylinder, and make sure that the values are correct. Compression (fully open throttle): Standard 1,020 - 1,275 kPa (10.4 - 13.0 kgf/cm 2 , 148 - 185 psi) Difference between cylinders 49 kPa (0.5 kgf/cm 2 , 7 psi) or less
13. After inspection, install the related parts in the reverse order of removal.

1. Before checking the idle speed, check the following item: Check the air cleaner element is free from clogging, ignition timing is correct, spark plugs are in good condition, and hoses are connected properly. Check the malfunction indicator light does not illuminate.
2. Warm up the engine.
3. Read the engine idle speed using Subaru Select Monitor. Refer to «READ CURRENT DATA FOR ENGINE (NORMAL MODE)»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/testing-diagnostics/#engine-controls-engine-diagnostics-h4so-except-sti__read-current-data-for-engine-normal) , OPERATION, Subaru Select Monitor.
4. Check the idle speed when no-loaded. (Headlight, heater fan, rear defroster, radiator fan, A/C and etc. are OFF) Idle speed (No load and at "P" or "N" position on AT model, or neutral position on MT model): 700±100 RPM (AT model) 650±100 RPM (MT model)
5. Check the idle speed when loaded. (Turn the A/C switch to "ON" and operate the compressor for at least one minute before measurement.)

Idle speed (A/C "ON" and at "P" or "N" position on AT model, or neutral position on MT model): 850±100 RPM

Note. Idle speed cannot be adjusted manually, because the idle speed is automatically adjusted, if the prescribed idle speed cannot be maintained, refer to the General On-board Diagnosis Table under "Engine Control System". Refer to BASIC DIAGNOSTIC PROCEDURE .

1. Before checking the ignition timing, check the following item: Check the air cleaner element is free from clogging, spark plugs are in good condition, and hoses are connected properly. Check the malfunction indicator light does not illuminate.
2. Warm up the engine.
3. Stop the engine, and turn the ignition switch to OFF.
4. Connect the timing light to #1 cylinder spark plug cord, and then light the timing mark with the timing light.
5. Start the engine and check the ignition timing at idle speed as shown below.

Ignition timing [BTDC/RPM]

15°±8°/700 (AT model)

10°±8°/650 (MT model)

Scheme 372

If the timing is not correct, check the ignition control system. Refer to BASIC DIAGNOSTIC PROCEDURE .

1. Warm up the engine.
2. Disconnect the brake booster vacuum hose from the intake manifold, and install the vacuum gauge.
3. Keep the engine at idle speed and read the vacuum gauge indication.

By observing the vacuum gauge needle movement, the internal condition of the engine can be diagnosed as described below.

Scheme 373

Intake manifold vacuum (at idling, A/C OFF)

Less than -60.0 kPa (-450 mmHg, -17.72 inHg)

VACUUM GAUGE INDICATION CHART

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1. Disconnect the ground cable from battery.
2. Remove the oil pressure switch. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/lubrication-system/#engine-lubrication-system-h4so-except-sti) , Oil Pressure Switch.
3. Install the oil pressure gauge to cylinder block.
4. Connect the ground cable to battery.
5. Start the engine, and measure the oil pressure. Engine oil pressure: Standard 98 kPa (1.0 kg/cm 2 , 14 psi) or more at 600 RPM 294 kPa (3.0 kg/cm 2 , 43 psi) or more at 5,000 RPM If the oil pressure is out of specification, check oil pump, oil filter and lubrication line. Refer to «INSPECTION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/lubrication-system/#engine-lubrication-system-h4so-except-sti) , Engine Lubrication System Trouble in General. If the oil pressure warning light is ON and oil pressure is within specification, check the oil pressure switch. Refer to «INSPECTION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/lubrication-system/#engine-lubrication-system-h4so-except-sti) , Engine Lubrication System Trouble in General. NOTE: Standard value is based on an engine oil temperature of 80°C (176°F).
6. After measuring the oil pressure, install the oil pressure switch. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/lubrication-system/#engine-lubrication-system-h4so-except-sti) , Oil Pressure Switch.

Note. Check or replace the fuel pump and fuel delivery line if the fuel pressure is out of the standard.

Scheme 376

1. Release the fuel pressure. Refer to «RELEASING OF FUEL PRESSURE»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/fuel-system/#fuel-injection-system-h4so-except-sti__releasing-of-fuel-pressure) , PROCEDURE, Fuel.
2. Open the fuel filler lid and remove the fuel filler cap.
3. Disconnect the fuel delivery hose from the fuel damper, and connect the fuel pressure gauge.
4. Start the engine.
5. Measure the fuel pressure after warming up the engine.

Note. The fuel pressure gauge registers 10 to 20 kPa (0.1 to 0.2 kg/cm 2 , 1 to 3 psi) higher than standard values during high-altitude operations.

Fuel pressure

Standard

339.5 - 360.5 kPa

(3.5 - 3.7 kg/cm 2 , 49 - 52 psi)

Note. Inspection and adjustment of valve clearance should be performed while engine is cold.

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1. Set the vehicle on a lift.
2. Lift up the vehicle.
3. Remove the under cover.
4. Lower the vehicle.
5. Disconnect the ground cable from battery.
6. Remove the timing belt cover LH.
7. Remove the fuel injector. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/fuel-system/#fuel-injection-system-h4so-except-sti) , Fuel Injector.
8. When inspecting #1 and #3 cylinders Disconnect the spark plug cords from spark plugs on RH side. Refer to «RH SIDE»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/ignition-system/#engine-ignition-system-h4so-except-sti__rh-side) , REMOVAL, Spark Plug. Place a suitable container under the vehicle. Disconnect the PCV hose from the rocker cover RH. Remove the bolts, then remove the rocker cover RH.
9. When inspecting #2 and #4 cylinders Disconnect the spark plug cords from spark plugs on LH side. Refer to «LH SIDE»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/ignition-system/#engine-ignition-system-h4so-except-sti__lh-side) , REMOVAL, Spark Plug. Place a suitable container under the vehicle. Disconnect the PCV hose from the rocker cover LH. Remove the bolts, then remove the rocker cover LH.
10. Set #1 cylinder piston to top dead center of compression stroke by rotating the crank pulley clockwise using the socket wrench. NOTE: When the arrow mark (A) on cam sprocket LH is at the top position, the #1 cylinder piston is at top dead center of the compression stroke.
11. Measure #1 cylinder valve clearance by using thickness gauge (A). NOTE: Insert the thickness gauge (A) in as horizontally as possible with respect to the valve stem end face. Lift up the vehicle, and then measure the exhaust valve clearances. Valve clearance (inspection value): Intake 0.20±0.04 mm (0.0079±0.0016 in) Exhaust 0.25±0.04 mm (0.0098±0.0016 in)
12. Measure the valve clearance in #3, #2 and #4 cylinder in the same measurement procedure as #1 cylinder in this order. NOTE: Be sure to set the cylinder pistons to their respective top dead centers on compression stroke before measuring valve clearances. By rotating the crank pulley clockwise every 180° from the state that #1 cylinder piston is on the top dead center of compression stroke, #3, #2 and #4 cylinder pistons come to the top dead center of compression stroke in this order.
13. If necessary, adjust the valve clearance. Refer to «ADJUSTMENT»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti__adjustment) , Valve Clearance.
14. After inspection, install the related parts in the reverse order of removal. NOTE: Use a new rocker cover gasket.

ADJUSTMENT

Note. Adjustment of valve clearance should be performed while engine is cold.

Scheme 380

1. Set #1 cylinder piston to top dead center of compression stroke by rotating the crank pulley clockwise using the socket wrench. NOTE: When the arrow mark (A) on cam sprocket LH is at the top position, the #1 cylinder piston is at top dead center of the compression stroke.
2. Adjust the #1 cylinder valve clearance. Loosen the valve rocker nut and screw. Set a suitable thickness gauge. While noting the valve clearance, tighten the valve rocker adjusting screw. When the specified valve clearance is obtained, tighten the valve rocker nut. NOTE: Insert a thickness gauge in a direction as horizontal as possible with respect to the valve stem end face. Lift up the vehicle and adjust the exhaust valve clearances. Valve clearance (adjustment value): Intake 0.20±0.04 mm (0.0079±0.0016 in) Exhaust 0.25±0.04 mm (0.0098±0.0016 in) Tightening torque: 9.75 N.m (1.0 kgf-m, 7.2 ft-lb)
3. Adjust the valve clearance in #3, #2 and #4 cylinder in the same adjustment procedure as #1 cylinder in this order. NOTE: Be sure to set the cylinder pistons to their respective top dead centers on compression stroke before adjusting valve clearances. By rotating the crank pulley clockwise every 180° from the state that #1 cylinder piston is on the top dead center of compression stroke, #3, #2 and #4 cylinder pistons come to the top dead center of compression stroke in this order.
4. Ensure the valve clearances of each cylinder are within specifications. If necessary, readjust the valve clearances.
5. After measurement, install the related parts in the reverse order of removal.

Note. Use a new rocker cover gasket.

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1. Set the vehicle on a lift.
2. Change the bolt installation position from (A) to (B), then open the front hood completely. Tightening torque: 7.5 N.m (0.8 kgf-m, 5.5 ft-lb)
3. Remove the V-belt covers.
4. Collect the refrigerant from A/C system. Refer to «PROCEDURE»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/automatic-hvac-system/#hvac-system-heater-ventilator-and-ac-except-sti) , Refrigerant Recovery Procedure.
5. Release the fuel pressure. Refer to «RELEASING OF FUEL PRESSURE»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/fuel-system/#fuel-injection-system-h4so-except-sti__releasing-of-fuel-pressure) , PROCEDURE, Fuel.
6. Remove the battery. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/charging-system/#starting-system-charging-system-h4so-except-sti) , Battery.
7. Remove the air intake duct, air cleaner case and air intake chamber. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-intake-system-h4so-except-sti) , Air Intake Duct. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-intake-system-h4so-except-sti) , Air Cleaner Case. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-intake-system-h4so-except-sti) , Air Intake Chamber.
8. Remove the under cover.
9. Remove the radiator from vehicle. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/cooling-system-mechanical/#engine-cooling-system-h4so-except-sti) , Radiator.
10. Disconnect the A/C pressure hoses from A/C compressor. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/automatic-hvac-system/#hvac-system-heater-ventilator-and-ac-except-sti) , Hose and Pipe.
11. Remove the air intake chamber stay.
12. Disconnect the following connectors and cables. Disconnect the front oxygen (A/F) sensor connector (A) and rear oxygen sensor connector (B) and remove the clip (C) fastening the harness. Remove the bolt, and disconnect the engine harness connector from the bulkhead harness connector and rear engine hanger. Generator connector and terminal A/C compressor connector Power steering pump switch connector
13. Disconnect the following hoses. Brake booster vacuum hose Heater inlet and outlet hoses
14. Remove the power steering pump. Remove the front side belts. Refer to «FRONT SIDE BELT»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti__front-side-belt) , REMOVAL, V-belt. Remove the bolts which secure the power steering pump to the bracket. Place the power steering pump on the right side wheel apron.
15. Lift up the vehicle.
16. Remove the front and center exhaust pipes. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/exhaust/#exhaust-system-h4so-except-sti__removal) , Front Exhaust Pipe.
17. Disconnect the ground cable on the engine side.
18. Remove the bolts and nuts which hold the lower side of transmission to the engine. AT MODEL MT MODEL
19. Remove the nuts which secure the engine mounting to the front crossmember.
20. Separate the torque converter clutch from the drive plate. (AT model) Lower the vehicle. Remove the service hole plug. Insert the wrench into the crank pulley bolt and rotate the crank pulley to remove the bolts which hold torque converter clutch to drive plate.
21. Remove the pitching stopper.
22. Disconnect the fuel delivery hose (A) and evaporation hose (B). Disconnect the quick connector of the fuel delivery hose by pushing the ST in the direction of the arrow. ST 42099AE000 QUICK CONNECTOR RELEASE Remove the clip and disconnect the evaporation hose from the pipe. CAUTION: Be careful not to spill fuel. Catch the fuel from hoses using a container or cloth.
23. Support the engine with a lifting device and wire ropes.
24. Support the transmission with a garage jack. CAUTION: Be sure to always perform this work, in order to prevent the transmission from lowering for its own weight.
25. Separation of engine and transmission CAUTION: Before removing the engine away from transmission, check to be sure no work has been overlooked. Remove the starter. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/charging-system/#starting-system-charging-system-h4so-except-sti) , Starter. Attach the ST to the torque converter clutch case. (AT model) ST 498277200 STOPPER SET Remove the bolts which hold upper side of transmission to engine. AT MODEL MT MODEL
26. Remove the engine from vehicle. Slightly raise the engine. Raise the transmission with garage jack. Move the engine horizontally until main shaft is withdrawn from clutch cover. (MT model) Slowly move the engine away from engine compartment. NOTE: Be careful not to damage adjacent parts or body panels with crank pulley, oil level gauge, etc.
27. Remove the engine mounting from the engine.

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1. Install the engine mounting onto the engine. Tightening torque: 35 N.m (3.6 kgf-m, 25.8 ft-lb)
2. Apply a small amount of grease to splines of main shaft. (MT model) Grease: NICHIMOLY N-130 or equivalent
3. Position the engine in engine compartment and align it with transmission. NOTE: Be careful not to damage adjacent parts or body panels with crank pulley, oil level gauge, etc.
4. Tighten the bolts which hold upper side of transmission to engine. Tightening torque: 50 N.m (5.1 kgf-m, 36.9 ft-lb) AT MODEL MT MODEL
5. Remove the lifting device and wire ropes.
6. Remove the garage jack.
7. Install the pitching stopper. Tightening torque: T1: 50 N.m (5.1 kgf-m, 36.9 ft-lb) T2: 58 N.m (5.9 kgf-m, 42.8 ft-lb)
8. Remove the ST from torque converter clutch case. (AT model) NOTE: Be careful not to drop the ST into the torque converter clutch case when removing the ST. ST 498277200 STOPPER SET
9. Install the starter. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/charging-system/#starting-system-charging-system-h4so-except-sti__installation) , Starter.
10. Install the torque converter clutch to drive plate. (AT model) Insert the wrench into the crank pulley bolt and rotate the crank pulley to install the bolts which hold torque converter clutch to drive plate. NOTE: Be careful not to drop bolts into the torque converter clutch case. Tightening torque: 25 N.m (2.5 kgf-m, 18.4 ft-lb) Install the service hole plug.
11. Install the power steering pump. Install the power steering pump. Tightening torque: Refer to " «COMPONENT»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) " of "Power Steering" for the tightening torque. Refer to «COMPONENT»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/manual-power-steering/#power-steering-system) , General Description. Connect the power steering pump switch connector. Install and adjust the front side belt. Refer to «FRONT SIDE BELT»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti__front-side-belt) , INSTALLATION, V-belt.
12. Lift up the vehicle.
13. Install the bolts and nuts which hold lower side of the transmission to engine. Tightening torque: 50 N.m (5.1 kgf-m, 36.9 ft-lb) AT MODEL MT MODEL
14. Install the nuts which hold the engine mounting to the crossmember. Tightening torque: 85 N.m (8.7 kgf-m, 62.7 ft-lb)
15. Connect the ground cable. Tightening torque: 7.5 N.m (0.8 kgf-m, 5.5 ft-lb)
16. Install the front and center exhaust pipe. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/exhaust/#exhaust-system-h4so-except-sti__installation) , Front Exhaust Pipe.
17. Lower the vehicle.
18. Connect the following hoses. Fuel delivery hose and evaporation hose Heater inlet and outlet hoses Brake booster vacuum hose
19. Connect the following connectors and terminals. Front oxygen (A/F) sensor connector Rear oxygen sensor connector Engine harness connectors Tightening torque: 6.4 N.m (0.7 kgf-m, 4.7 ft-lb) Generator connector and terminal Tightening torque: 15 N.m (1.5 kgf-m, 11.1 ft-lb) A/C compressor connector
20. Install the air intake chamber stay. Tightening torque: 16 N.m (1.6 kgf-m, 11.8 ft-lb)
21. Install the A/C pressure hoses. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/automatic-hvac-system/#hvac-system-heater-ventilator-and-ac-except-sti) , Hose and Pipe.
22. Install the radiator to vehicle. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/cooling-system-mechanical/#engine-cooling-system-h4so-except-sti) , Radiator.
23. Install the air intake duct, air cleaner case and air intake chamber. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-intake-system-h4so-except-sti) , Air Intake Duct. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-intake-system-h4so-except-sti) , Air Cleaner Case. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-intake-system-h4so-except-sti) , Air Intake Chamber.
24. Install the under cover.
25. Install the battery. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/charging-system/#starting-system-charging-system-h4so-except-sti) , Battery.
26. Fill engine coolant. Refer to «FILLING OF ENGINE COOLANT»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/cooling-system-mechanical/#engine-cooling-system-h4so-except-sti) , REPLACEMENT, Engine Coolant.
27. Check the ATF level and replenish it if necessary. (AT model) Refer to «INSPECTION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/automatic-trans/#automatic-transmission-4at-except-sti__inspection) , Automatic Transmission Fluid.
28. Charge the A/C system with refrigerant. Refer to «PROCEDURE»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/automatic-hvac-system/#hvac-system-heater-ventilator-and-ac-except-sti) , Refrigerant Charging Procedure.
29. Install the V-belt cover. Tightening torque: 13 N.m (1.3 kgf-m, 9.6 ft-lb)
30. Change the bolt installation position from (B) to (A), then close the front hood.

Tightening torque

7.5 N.m (0.8 kgf-m, 5.5 ft-lb)

1. Check that pipes, hoses, connectors and clamps are installed firmly.
2. Check the engine coolant is at specified level.
3. Check that the ATF is at specified level. (AT model)
4. Start the engine and check for exhaust gas, engine coolant, leaks of fuel, etc. Also check for noise and vibrations.

REMOVAL

1. Remove the engine assembly. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti__removal) , Engine Assembly.
2. Remove the engine mounting from the engine assembly.

INSTALLATION

Install in the reverse order of removal.

Tightening torque

Engine mounting

35 N.m (3.6 kgf-m, 25.8 ft-lb)

Make sure that no crack or other damages do not exist.

Scheme 406

1. After removing the engine from body, secure it to ST in the following procedure. ST1 498457000 ENGINE STAND ADAPTER RH ST2 498457100 ENGINE STAND ADAPTER LH ST3 499817100 ENGINE STAND
2. In this information the procedures described under each index are all connected and stated in order. The procedure for overhauling of the engine will be completed when you go through all steps in the process.

Therefore, in this information, to conduct the particular procedure within the flow of an area, you need to go back and conduct the procedure described previously in order to do that particular procedure.

Note. Perform the work with the engine installed to body when replacing a single part.

FRONT SIDE BELT

1. Remove the V-belt covers.
2. Remove the air intake duct. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-intake-system-h4so-except-sti) , Air Intake Duct.
3. Loosen the bolt (A).
4. Loosen the slider bolt (B).
5. Remove the front side belt (C).

Scheme 407

REAR SIDE BELT

1. Remove the front side belts. Refer to «FRONT SIDE BELT»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti__front-side-belt) , REMOVAL, V-belt.
2. Cut the rear side belt with a wire cutter, etc. and discard.

Scheme 408

1. Wipe off any dust, oil and water on the groove of each pulley with cloth.
2. Install the front side belt (C), and adjust the slider bolt (B) so as to obtain the specified belt tension. Refer to «INSPECTION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.
3. Tighten the bolt (A).
4. Tighten the slider bolt (B). Tightening torque: Bolt (A) 25 N.m (2.5 kgf-m, 18.4 ft-lb) Slider bolt (B) 8 N.m (0.8 kgf-m, 5.9 ft-lb)
5. Install the air intake duct. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-intake-system-h4so-except-sti) , Air Intake Duct.
6. Install the V-belt cover.

Tightening torque

13 N.m (1.3 kgf-m, 9.6 ft-lb)

Scheme 409

Scheme 410

Scheme 411

Scheme 412

Scheme 413

Scheme 414

Scheme 415

Scheme 416

Scheme 417

Scheme 418

Scheme 419

Scheme 420

Scheme 421

Scheme 422

Scheme 423

Scheme 424

Scheme 425

Scheme 426

Scheme 427

Scheme 428

Scheme 429

1. Wipe off any dust, oil and water on the groove of each pulley with cloth.
2. Wipe off any oil, water, dirt, and rust on the front of the crank pulley with cloth.
3. Slowly turn the crank pulley clockwise so that the service hole of the crank pulley comes around the top. CAUTION: Do not turn the crank pulley counterclockwise.
4. Hook a new rear side belt on the A/C compressor pulley.
5. As shown in the figure, insert the claw of the belt stopper (A) to the lower hole (B) of the compressor bracket, then attach with bolt (C).
6. Place the belt guide while aligning it with the belt line of the crank pulley on the front side belt side.
7. Insert the belt guide holder into the service hole of the crank pulley so that the belt guide comes in between. NOTE: Place the belt guide holder with the longer side up.
8. Slowly turn the crank pulley clockwise until the belt guide comes to approximately 45°.
9. Place the rib surface of the rear side belt into the crank pulley groove, so that the rear side belt comes in between the belt guide holder. CAUTION: When it is difficult to place the rear side belt to the crank pulley groove, pull out the belt guide holder half way, then place the rear side belt into the groove so that it comes in between the belt guide holder.
10. Place the tool through the loop of the rear side belt, and set on the crank pulley bolt.
11. While checking the following, slowly turn the crank pulley approximately 90° clockwise so that the belt guide comes to the position shown in the figure. CAUTION: When turning the crank pulley, always make sure that the belt guide is not off from the crank pulley groove. The rib of the rear side belt is securely placed on the groove of the A/C compressor pulley. The rib of the rear side belt is securely placed on the groove of the crank pulley. The surface of the rear side belt is held by the belt stopper. The rear side belt is securely placed on the belt guide.
12. While checking the following, slowly turn the crank pulley approximately 90° clockwise so that the belt guide comes to the position shown in the figure. The rear side belt is not twisted. The rib of the rear side belt is securely placed on the groove of the A/C compressor pulley. The rib of the rear side belt is securely placed on the groove of the crank pulley. The surface of the rear side belt is held by the belt stopper. The rear side belt is securely placed on the belt guide.
13. Slowly turn the crank pulley clockwise, and install the rear side belt. CAUTION: Be careful that the total of procedures 8), 11), 12) and 13) does not exceed 330°; failure to do so may cause damage to the rear side belt and fall of the belt guide holder.
14. Remove the belt guide and belt guide holder from the crank pulley.
15. Remove the belt stopper from the compressor bracket. CAUTION: Always remove the belt stopper; failure to do so may cause smoke, fire, or belt cutting.
16. Make sure that the belt rib is securely installed on the groove of each pulley, then turn the crank pulley slowly, twice in the clockwise direction, to seat the rear side belt properly.
17. Discard the provided tools (belt stopper, belt guide, belt guide holder, and bolt) that are used.
18. Install the front side belt. Refer to «FRONT SIDE BELT»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti__front-side-belt) , INSTALLATION, V-belt.

1. Replace the front side belt, if crack, fraying or wear is found.
2. Check the front side belt tension and adjust it if necessary by changing the generator installing position.

Front side belt tension (with belt tension gauge)

When installing new parts

640 - 780 N (65 - 80 kgf, 144 - 175 lbf)

At inspection

490 - 640 N (50 - 65 kgf, 110 - 144 lbf)

Scheme 430

Front side belt tension (without belt tension gauge)

When installing new parts

7 - 9 mm (0.276 - 0.354 in)

At inspection

9 - 11 mm (0.354 - 0.433 in)

Scheme 431

If cracks, fraying or wear is found, and when abnormal noise is produced, replace the rear side belt.

Note. Because the rear side belt is a stretch type belt, it is not necessary to check deflection and tension.

Note. Perform the work with the engine installed to body when replacing a single part.

Scheme 432

1. Remove the V-belts. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.
2. Use the ST to lock the crank pulley, and remove the crank pulley bolts. ST 499977400 CRANK PULLEY WRENCH (AT MODEL) ST 499977100 CRANK PULLEY WRENCH (MT MODEL)
3. Remove the crank pulley.

AT MODEL

1. Install the crank pulley.
2. Use the ST to lock the crank pulley, and attach the crank pulley bolts. ST 499977400 CRANK PULLEY WRENCH Clean the crankshaft thread using compressed air. Apply engine oil to the crank pulley bolt seat and thread. Tighten the bolts temporarily with tightening torque of 44 N.m (4.5 kgf-m, 32.5 ft-lb). Tighten the crank pulley bolts. Tightening torque: 130 N.m (13.3 kgf-m, 95.9 ft-lb)
3. Check that the tightening angle of the crank pulley bolt is 45° or more. Perform the following procedure when less than 45°. CAUTION: If the tightening angle of crank pulley bolt is less than 45°, the bolt is damaged. In this case, the bolt must be replaced. Replace the crank pulley bolts and clean them. Crank pulley bolt: Part No. 12369AA011 Clean the crankshaft thread using compressed air. Apply engine oil to the crank pulley bolt seat and thread. Tighten the bolts temporarily with tightening torque of 44 N.m (4.5 kgf-m, 32.5 ft-lb). Tighten the crank pulley bolts by 45° to 60°. NOTE: Conduct the tightening procedures by confirming the turning angle of crank pulley bolt referring to the gauge indicated on timing belt cover.
4. Install the V-belts. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.

MT MODEL

1. Install the crank pulley.
2. Use the ST to lock the crank pulley, and attach the crank pulley bolts. ST 499977100 CRANK PULLEY WRENCH Clean the crankshaft thread using compressed air. Apply engine oil to the crank pulley bolt seat and thread. Tighten the bolts temporarily with tightening torque of 44 N.m (4.5 kgf-m, 32.5 ft-lb). Tighten the crank pulley bolts. Tightening torque: 180 N.m (18.4 kgf-m, 132.8 ft-lb)
3. Check that the tightening angle of the crank pulley bolt is 65° or more. Perform the following procedure when less than 65°. CAUTION: If the tightening angle of crank pulley bolt is less than 65°, the bolt is damaged. In this case, the bolt must be replaced. Replace the crank pulley bolts and clean them. Crank pulley bolt: Part No. 12369AA011 Clean the crankshaft thread using compressed air. Apply engine oil to the crank pulley bolt seat and thread. Tighten the bolts temporarily with tightening torque of 44 N.m (4.5 kgf-m, 32.5 ft-lb). Tighten the crank pulley bolts by 65° to 75°. NOTE: Conduct the tightening procedures by confirming the turning angle of crank pulley bolt referring to the gauge indicated on timing belt cover.
4. Install the V-belts. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.

1. Make sure the V-belt is not worn or otherwise damaged.
2. Check the tension of the front side belt. Refer to «INSPECTION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.

Note. Perform the work with the engine installed to body when replacing a single part.

1. Remove the V-belts. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.
2. Remove the crank pulley. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Crank Pulley.
3. Remove the timing belt cover LH.
4. Remove the front timing belt cover.

Scheme 433

Scheme 434

1. Install the front timing belt cover. Tightening torque: 5 N.m (0.5 kgf-m, 3.7 ft-lb)
2. Install the timing belt cover LH. Tightening torque: 5 N.m (0.5 kgf-m, 3.7 ft-lb)
3. Install the crank pulley. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Crank Pulley.
4. Install the V-belts. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.

Check the timing belt cover for damage.

Note. Perform the work with the engine installed to body when replacing a single part. For operation procedures, refer to " TIMING BELT ". Refer to TIMING BELT .

Scheme 435

Scheme 436

Scheme 437

Scheme 438

Scheme 439

Scheme 440

1. Remove the V-belts. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.
2. Remove the crank pulley. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Crank Pulley.
3. Remove the timing belt cover. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt Cover.
4. Remove the timing belt guide. (MT model)
5. If the alignment mark or arrow mark (which indicates the direction of rotation) on timing belt fade away, put new marks before removing the timing belt as shown in procedures below. Use the ST to turn crankshaft. Align the mark (a) of sprocket to the mark (b) of oil pump, and then ensure the right side cam sprocket mark (c), cam cap and cylinder head matching surface (d) or left side cam sprocket mark (e), timing belt cover notch (f) are properly adjusted. ST 499987500 CRANKSHAFT SOCKET Using white paint, put an alignment mark or an arrow mark on timing belts in relation to the crank sprocket and cam sprockets. Z 1 : 46.8 teeth Z 2 : 43.7 teeth
6. Remove the belt idler (A).
7. Remove the belt idler No. 2 (B).
8. Remove the timing belt.

Scheme 441

Scheme 442

1. Remove the belt idler.
2. Remove the automatic belt tension adjuster assembly.

Scheme 443

Scheme 444

Scheme 445

Scheme 446

1. Prepare for installation of the automatic belt tension adjuster assembly. CAUTION: Always use a vertical type pressing tool to move the adjuster rod down. Do not use a lateral type vise. Push the adjuster rod vertically. Press-in the push adjuster rod gradually taking three minutes or more. Do not allow press pressure to exceed 9,807 N (1,000 kgf, 2,205 lb). Push in the adjuster rod to the end face of the cylinder. However, do not push in the adjuster rod below the end face of the cylinder. Doing so may damage the cylinder. Do not release the press pressure until stopper pin is completely inserted. Attach the automatic belt tension adjuster assembly to vertical pressing tool. Slowly push in the adjuster rod with a pressure of 165 N (16.8 kgf, 37.1 lb) or more until the adjuster rod is aligned with the stopper pin hole in the cylinder. With a 2 mm (0.08 in) dia. stopper pin or a 2 mm (0.08 in) (nominal) dia. hex wrench inserted into the stopper pin hole in cylinder, secure the adjuster rod.
2. Install the automatic belt tension adjuster assembly. Tightening torque: 39 N.m (4.0 kgf-m, 28.8 ft-lb)
3. Install the belt idlers.

Tightening torque

39 N.m (4.0 kgf-m, 28.8 ft-lb)

Scheme 447

Scheme 448

Scheme 449

Scheme 450

Scheme 451

Scheme 452

Scheme 453

1. Prepare for installation of the automatic belt tension adjuster assembly. Refer to «AUTOMATIC BELT TENSION ADJUSTER ASSEMBLY AND BELT IDLER»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , INSTALLATION, Timing Belt.
2. Align the mark (B) on oil pump with the mark (A) on crank sprocket.
3. Turn the camshaft sprocket No. 2 using ST1, and turn the camshaft sprocket No. 1 using ST2 so that their alignment marks (A) come to top positions. ST 1 18231AA010 CAM SPROCKET WRENCH NOTE: CAM SPROCKET WRENCH (499207100) can also be used. ST2 499207400 CAM SPROCKET WRENCH
4. While aligning the alignment mark (B) on timing belt with the mark (A) on sprockets, position the timing belt properly.
5. Install the belt idler No. 2 (B). Tightening torque: 39 N.m (4.0 kgf-m, 28.8 ft-lb)
6. Install the belt idler (A). Tightening torque: 39 N.m (4.0 kgf-m, 28.8 ft-lb)
7. After ensuring the marks on timing belt and camshaft sprockets are aligned, remove the stopper pin from belt tension adjuster.
8. Install the timing belt guide. (MT model) Temporarily tighten the bolts mounting the timing belt guide. Check and adjust the clearance between timing belt and timing belt guide by using thickness gauge. Clearance: 1.0±0.5 mm (0.039±0.020 in) Tighten the bolts mounting the timing belt guide. Tightening torque: 9.75 N.m (1.0 kgf-m, 7.2 ft-lb)
9. Install the timing belt cover. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt Cover.
10. Install the crank pulley. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Crank Pulley.
11. Install the V-belts. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.

TIMING BELT

1. Check the timing belt teeth for breaks, cracks or wear. If any fault is found, replace the timing belt.
2. Check the condition on the back surface of the timing belt. If cracks are found, replace the timing belt.

In radial diameter h

60 mm (2.36 in) or more

Scheme 454

AUTOMATIC BELT TENSION ADJUSTER

1. Visually check the oil seals for leaks, and rod ends for abnormal wear and scratches. If necessary, replace the automatic belt tension adjuster assembly. NOTE: Slight traces of oil at rod's oil seal does not indicate a problem.
2. Check that the adjuster rod does not move when a pressure of 165 N (16.8 kgf, 37.1 lb) is applied to it. This is to check adjuster rod stiffness.
3. If the adjuster rod is not stiff and moves freely when applying 165 N (16.8 kgf, 37.1 lb), check it using the following procedures: Slowly press the adjuster rod down to the end surface of cylinder. Repeat this operation two to three times. With the adjuster rod moved all the way up, apply a pressure of 165 N (16.8 kgf, 37.1 lb) to it, and check the adjuster rod stiffness. If the adjuster rod is not stiff and moves down, replace the automatic belt tension adjuster assembly with a new part. CAUTION: Always use a vertical type pressing tool to move the adjuster rod down. Do not use a lateral type vise. Push the adjuster rod vertically. Press the adjuster rod gradually taking three minutes or more. Do not allow press pressure to exceed 9,807 N (1,000 kgf, 2,205 lb). Push in the adjuster rod to the end face of the cylinder. However, do not press the adjuster rod below the end face of the cylinder. Doing so may damage the cylinder.
4. Measure the amount of rod protrusion "H" from the end surface of the body. If it is not within specifications, replace the automatic belt tension adjuster assembly with a new part.

Amount of rod protrusion H

5.2 - 6.2 mm (0.204 - 0.244 in)

Scheme 455

BELT TENSION PULLEY

1. Check the mating surfaces of timing belt and contact point of adjuster rod for abnormal wear or scratches. Replace the automatic belt tension adjuster assembly with a new part if faulty.
2. Check the belt tension pulley for smooth rotation. Replace the automatic belt tension adjuster assembly with a new part if abnormal noise or excessive play occurs.
3. Check the belt tension pulley for grease leakage.

BELT IDLER

1. Check the belt idler for smooth rotation. Replace if noise or excessive play occurs.
2. Check the outer contacting surfaces of idler pulley for abnormal wear and scratches.
3. Check the belt idler for grease leakage.

Note. Perform the work with the engine installed to body when replacing a single part.

1. Remove the V-belts. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.
2. Remove the crank pulley. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Crank Pulley.
3. Remove the timing belt cover. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt Cover.
4. Remove the timing belt. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt.
5. Remove the camshaft position sensor. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/fuel-system/#fuel-injection-system-h4so-except-sti) , Camshaft Position Sensor.
6. Fasten the cam sprocket and remove from the camshaft using ST.

ST 18231AA010 CAM SPROCKET WRENCH

Note. CAM SPROCKET WRENCH (499207100) can also be used.

Scheme 456

ST 499207400 CAM SPROCKET WRENCH

Scheme 457

1. Fasten the cam sprocket and install to the camshaft using ST. NOTE: Do not confuse cam sprockets (LH) and (RH) during installation. They should be distinguished by the L or R indication. ST 18231AA010 CAM SPROCKET WRENCH NOTE: CAMSHAFT SPROCKET WRENCH (499207100) can also be used. Tightening torque: 78 N.m (8.0 kgf-m, 57.5 ft-lb) ST 499207400 CAM SPROCKET WRENCH Tightening torque: 78 N.m (8.0 kgf-m, 57.5 ft-lb)
2. Install the camshaft position sensor. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/fuel-system/#fuel-injection-system-h4so-except-sti) , Camshaft Position Sensor.
3. Install the timing belt. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt.
4. Install the timing belt cover. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt Cover.
5. Install the crank pulley. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Crank Pulley.
6. Install the V-belts. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.

1. Check the cam sprocket teeth for abnormal wear and scratches.
2. Make sure there is no free play between cam sprocket and key.
3. Check the cam sprocket protrusion used for sensor for damage and contamination of foreign matter.

Note. Perform the work with the engine installed to body when replacing a single part.

1. Remove the V-belts. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.
2. Remove the crank pulley. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Crank Pulley.
3. Remove the timing belt cover. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt Cover.
4. Remove the timing belt. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt.
5. Remove the crank sprocket.

Scheme 458

1. Install the crank sprocket.
2. Install the timing belt. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt.
3. Install the timing belt cover. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt Cover.
4. Install the crank pulley. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Crank Pulley.
5. Install the V-belts. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.

1. Check the crank sprocket teeth for abnormal wear and scratches.
2. Make sure there is no free play between crank sprocket and key.
3. Check the crank sprocket protrusion used for sensor for damage and contamination of foreign matter.

Note. Perform the work with the engine installed to body when replacing a single part. Refer to "Valve Clearance" for preparation procedures. Refer to VALVE CLEARANCE .

1. Remove the high tension cord.
2. Disconnect the PCV hose and remove the rocker cover.
3. Remove the valve rocker assembly.

Scheme 459

Scheme 460

Scheme 461

1. Use the ST to rotate the spring stopper in the direction of the arrow to remove it from adjuster pin. ST 18258AA000 SPRING INSTALLER
2. Remove the bolts (a) through (j) in alphabetical sequence. NOTE: Leave two or three threads of bolts (i) and (j) engaged in order to retain the valve rocker assembly.
3. Remove the valve rocker assembly.

Note. Set the ST in the position shown in the drawing to remove the intake valve rocker assembly.

ST 18354AA000 VALVE ROCKER HOLDER

Scheme 462

Scheme 463

Scheme 464

Scheme 465

Scheme 466

1. Install the valve rocker assembly. Temporarily tighten the bolts equally in alphabetical order as shown in the figure. NOTE: Do not temporarily tighten the bolts (i) and (j). Set the ST in the position shown in the drawing to mount the intake valve rocker assembly. ST 18354AA000 VALVE ROCKER HOLDER Tighten the bolts (a) through (h) to specified torque. Tightening torque: 25 N.m (2.5 kgf-m, 18.4 ft-lb) Tighten the bolts (i) through (j) to specified torque. Tightening torque: 6 N.m (0.6 kgf-m, 4.4 ft-lb) Use the ST to rotate the spring stopper in the direction of the arrow to fasten the adjuster pin. ST 18258AA000 SPRING INSTALLER
2. Remove the timing belt cover LH.
3. Adjust the valve clearance. Refer to «ADJUSTMENT»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti__adjustment) , Valve Clearance.
4. Install the timing belt cover LH.
5. Install the rocker cover. Install the rocker cover gasket to the rocker cover. NOTE: Use a new rocker cover gasket. Temporarily tighten the bolts in alphabetical order shown in the figure, tighten them in two stages. Tightening torque: First 6.4 N.m (0.7 kgf-m, 4.7 ft-lb) Second (only (a) and (b) are tightened) 6.4 N.m (0.7 kgf-m, 4.7 ft-lb) RH side LH side Connect the PCV hose.
6. Install the high tension cord.

DISASSEMBLY

Note. Intake valve rocker assembly cannot be disassembled.

1. Remove the exhaust valve rocker arm from the rocker shaft. NOTE: Keep all the removed parts in order for re-installing in their original positions.
2. Remove the nut and adjusting screw from exhaust valve rocker.

ASSEMBLY

Note. Intake valve rocker assembly cannot be disassembled.

1. Install the adjusting screw and nut to the exhaust valve rocker.
2. Insert the exhaust valve rocker arm to rocker shaft.

Note. Valve rocker arms, and rocker shaft have identification marks. Make sure the parts with same markings are properly assembled.

INTAKE VALVE ROCKER ASSEMBLY

1. If the roller or valve contact surface of valve rocker arm is worn or dented excessively, replace the valve rocker assembly.
2. Check that the valve rocker arm roller rotates smoothly. If not, replace the valve rocker assembly.

Scheme 467

Scheme 468

1. Measure the inner diameter of valve rocker arm and outer diameter of valve rocker shaft, and confirm the difference (oil clearance) between the two values. Clearance between arm and shaft: Standard 0.020 - 0.054 mm (0.0008 - 0.0021 in)
2. If the oil clearance exceeds the limit, replace the valve rocker arm or shaft, whichever shows the greater amount of wear. Rocker arm inside diameter: 22.020 - 22.041 mm (0.8669 - 0.8678 in) Rocker shaft diameter: 21.987 - 22.000 mm (0.8656 - 0.8661 in)
3. If the roller or valve contact surface of valve rocker arm is worn or dented excessively, replace the valve rocker arm.
4. Check that the valve rocker arm roller rotates smoothly. If not, replace the valve rocker arm.

Note. Perform the work with the engine installed to body when replacing a single part. Refer to "Valve Clearance" for preparation procedures. Refer to VALVE CLEARANCE .

Scheme 469

Scheme 470

Scheme 471

Scheme 472

Scheme 473

1. Remove the V-belts. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.
2. Remove the crank pulley. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Crank Pulley.
3. Remove the timing belt cover. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt Cover.
4. Remove the timing belt. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt.
5. Remove the cam sprocket. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Cam Sprocket.
6. Remove the timing belt cover No. 2 LH.
7. Remove the timing belt cover No. 2 RH. NOTE: Do not damage or lose the seal rubber when removing the timing belt covers.
8. Remove the tensioner bracket.
9. Remove the camshaft position sensor support. (LH side only)
10. Remove the valve rocker assembly. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Valve Rocker Assembly.
11. Remove the camshaft cap. Remove the bolts (a) and (b) in alphabetical sequence. Equally loosen the bolts (c) through (j) all the way in alphabetical sequence. Remove the bolts (k) through (p) in alphabetical sequence using ST. ST 499497000 TORX® PLUS Remove the camshaft cap.
12. Remove the camshaft.
13. Remove the oil seal.
14. Remove the plug from rear side of camshaft. CAUTION: Do not scratch the journal surface when removing the oil seal.
15. Similarly, remove the camshaft RH and related parts.

Scheme 474

Scheme 475

Scheme 476

Scheme 477

Scheme 478

Scheme 479

Scheme 480

Scheme 481

Scheme 482

Scheme 483

1. Apply a thin coat of engine oil to camshaft journals, and install the camshaft.
2. Install the camshaft cap. Apply liquid gasket to the mating surfaces of camshaft cap. NOTE: Install within 5 min. after applying liquid gasket. Liquid gasket: THREE BOND 1217G (Part No. K0877Y0100) or equivalent NOTE: Apply a coat of liquid gasket of 3 mm (0.12 in) in diameter (A) along the edge (B) of camshaft cap (C) mating surface. Temporarily tighten the bolts (a) through (d) in alphabetical sequence. Install the valve rocker assembly. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Valve Rocker Assembly. Tighten the TORX® bolts (e) through (j) in alphabetical sequence using the ST. ST 499497000 TORX® PLUS Tightening torque: 18 N.m (1.8 kgf-m, 13.3 ft-lb) Tighten the bolts (k) through (r) in alphabetical sequence. Tightening torque: 9.75 N.m (1.0 kgf-m, 7.2 ft-lb) Tighten the bolts (s) and (t) in alphabetical sequence. NOTE: Use a new seal washer. Install and tighten the seal washer to the bolt. Tightening torque: 9.75 N.m (1.0 kgf-m, 7.2 ft-lb)
3. Apply a coat of engine oil to camshaft oil seal periphery and oil seal lips and install the oil seal (A) on camshaft using ST1 and ST2. NOTE: Use a new oil seal. ST1 499597000 OIL SEAL GUIDE ST2 499587500 OIL SEAL INSTALLER
4. Apply a coat of engine oil to plug periphery and install the plug (A) using ST. ST 499587700 CAMSHAFT OIL SEAL INSTALLER
5. Install the camshaft position sensor support. (LH side only) Tightening torque: 6.4 N.m (0.7 kgf-m, 4.7 ft-lb)
6. Similarly, install the parts on right-hand side.
7. Install the tensioner bracket. Tightening torque: 24.5 N.m (2.5 kgf-m, 18.1 ft-lb)
8. Install the timing belt cover No. 2 RH. Tightening torque: 5 N.m (0.5 kgf-m, 3.7 ft-lb)
9. Install the timing belt cover No. 2 LH. Tightening torque: 5 N.m (0.5 kgf-m, 3.7 ft-lb)
10. Install the cam sprocket. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Cam Sprocket.
11. Install the timing belt. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt.
12. Adjust the valve clearance. Refer to «ADJUSTMENT»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti__adjustment) , Valve Clearance.
13. Install the rocker cover. Install the rocker cover gasket to the rocker cover. NOTE: Use a new rocker cover gasket. Temporarily tighten the bolts in alphabetical order shown in the figure, tighten them in two stages. Tightening torque: First 6.4 N.m (0.7 kgf-m, 4.7 ft-lb) Second (only (a) and (b) are tightened) 6.4 N.m (0.7 kgf-m, 4.7 ft-lb) RH side LH side Connect the PCV hose.
14. Install the high tension cord.
15. Install the timing belt cover. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt Cover.
16. Install the crank pulley. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Crank Pulley.
17. Install the V-belts. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.

Scheme 484

Scheme 485

1. Measure the bend, and repair or replace if necessary. Camshaft bend limit: 0.025 mm (0.00098 in)
2. Check the journal for damage and wear. Replace if faulty.
3. Check the cam face condition, and remove the minor faults by grinding with oil stone. If offset wear occurs, replace it.
4. Measure the cam lobe height H, cam base circle diameter A and base circle step of adjacent intake cams (low speed and high speed). If it exceeds the standard or offset wear occurs, replace it. Cam lobe height H: CAM LOBE HEIGHT SPECIFICATION Unit: mm (in) Intake Constant Standard 40.075 - 40.175 (1.5778 - 1.5817) Low speed Standard 35.496 - 35.596 (1.3975 - 1.4014) High speed Standard 40.315 - 40.415 (1.5872 - 1.5911) Exhaust Standard 39.289 - 39.389 (1.5468 - 1.5507) Cam base circle diameter A: Standard 34.00 mm (1.3386 in) Base circle step of adjacent intake cams (low speed and high speed): Standard 0.03 mm (0.001 in) or less
5. Measure the outer diameter of camshaft journal and inner diameter of cylinder head journal, and check the difference (oil clearance) between the two values. If the oil clearance is not within the standard, replace the camshaft or cylinder head as necessary. CAMSHAFT JOURNAL SPECIFICATION Unit: mm (in) Oil clearance Standard 0.055 - 0.090 (0.0022 - 0.0035) Camshaft journal O.D. 31.928 - 31.945 (1.2570 - 1.2577) Journal hole I.D. 32.000 - 32.018 (1.2598 - 1.2605)
6. Measure the thrust clearance with setting the dial gauge at end surface of camshaft. If the thrust clearance is not within the standard or there is offset wear, replace the camshaft caps and cylinder head as a set. If necessary, replace the camshaft.

Camshaft thrust clearance

Standard

0.030 - 0.090 mm (0.0012 - 0.0035 in)

Note. Perform the work with the engine installed to body when replacing a single part. Refer to "Valve Clearance" for preparation procedures. Refer to VALVE CLEARANCE . When performing the work with the engine installed to body, the following parts must also be removed/installed.

1. Front exhaust pipe Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/exhaust/#exhaust-system-h4so-except-sti__removal) , Front Exhaust Pipe. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/exhaust/#exhaust-system-h4so-except-sti__installation) , Front Exhaust Pipe.

Scheme 486

1. Remove the V-belts. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.
2. Remove the intake manifold. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/fuel-system/#fuel-injection-system-h4so-except-sti) , Intake Manifold.
3. Remove the crank pulley. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Crank Pulley.
4. Remove the timing belt cover. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt Cover.
5. Remove the timing belt. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt.
6. Remove the cam sprocket. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Cam Sprocket.
7. Remove the bolts which secure A/C compressor bracket to cylinder head.
8. Remove the valve rocker assembly. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Valve Rocker Assembly.
9. Remove the camshaft. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Camshaft.
10. Remove the oil level gauge guide. (LH side)
11. Remove the cylinder head bolts in alphabetical sequence as shown in the figure. NOTE: Leave bolts (a) and (c) engaged by three or four threads to prevent the cylinder head from falling.
12. While tapping the cylinder head with a plastic hammer, separate it from cylinder block. Remove the bolts (a) and (c) to remove cylinder head.
13. Remove the cylinder head gasket. CAUTION: Be careful not to scratch the mating surface of cylinder head and cylinder block.
14. Similarly, remove the right side cylinder head.

Scheme 487

1. Install the cylinder head and gaskets on cylinder block. CAUTION: Be careful not to scratch the mating surface of cylinder block and cylinder head. NOTE: Use a new cylinder head gasket.
2. Tighten the cylinder head bolts. Apply a thin coat of engine oil to washer and bolt thread. Tighten all bolts to 29 N.m (3.0 kgf-m, 21.4 ft-lb) in alphabetical order. Retighten all bolts to 69 N.m (7.0 kgf-m, 50.9 ft-lb) in alphabetical order. Loosen all the bolts by 180° in the reverse order of installing, and loosen them further by 180°. Tighten all bolts to 42 N.m (4.3 kgf-m, 31.0 ft-lb) in alphabetical order. Tighten all bolts by 80 to 90° in alphabetical order. Tighten all bolts by 40 to 45° in alphabetical order. CAUTION: The tightening angle of the bolt should not exceed 45°. Further tighten the bolts (a) and (b) by 40 - 45°. CAUTION: Make sure the total "re-tightening angle" of the step (7) and (8) does not exceed 90°.
3. Install the oil level gauge guide. (LH side) Tightening torque: 6.4 N.m (0.7 kgf-m, 4.7 ft-lb)
4. Install the camshaft. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Camshaft.
5. Install the valve rocker assembly. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Valve Rocker Assembly.
6. Install the A/C compressor bracket on cylinder head. Tightening torque: 36 N.m (3.7 kgf-m, 26.6 ft-lb)
7. Install the cam sprocket. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Cam Sprocket.
8. Install the timing belt. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt.
9. Adjust the valve clearance. Refer to «ADJUSTMENT»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti__adjustment) , Valve Clearance.
10. Install the rocker cover. Install the rocker cover gasket to the rocker cover. NOTE: Use a new rocker cover gasket. Temporarily tighten the bolts in alphabetical order shown in the figure, tighten them in two stages. Tightening torque: First 6.4 N.m (0.7 kgf-m, 4.7 ft-lb) Second (only (a) and (b) are tightened) 6.4 N.m (0.7 kgf-m, 4.7 ft-lb) RH side LH side
11. Install the timing belt cover. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt Cover.
12. Install the crank pulley. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Crank Pulley.
13. Install the intake manifold. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/fuel-system/#fuel-injection-system-h4so-except-sti) , Intake Manifold.
14. Install the V-belts. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.

1. Place the cylinder head on the ST. ST 498267800 CYLINDER HEAD TABLE
2. Compress the valve spring and remove the valve spring retainer key using ST. Remove each valve and valve spring.

ST 499718000 VALVE SPRING REMOVER

Scheme 488

Note. Keep all the removed parts in order for re-installing in their original positions. Mark each valve to prevent confusion. Pay careful attention not to damage the lips of intake valve oil seals and exhaust valve oil seals. For removal and installation procedures of the valve guide, intake valve oil seal and exhaust valve oil seal, Refer to "INSPECTION". Refer to VALVE GUIDE , INSPECTION, Cylinder Head. Refer to INTAKE AND EXHAUST VALVE OIL SEAL , INSPECTION, Cylinder Head.

Scheme 489

Scheme 490

1. Install the valve spring and valve. Coat the stem of each valve with engine oil and insert the valve into valve guide. NOTE: When inserting the valve into valve guide, use special care not to damage the oil seal lip. Set the cylinder head on ST. ST 498267800 CYLINDER HEAD TABLE Install the valve spring and retainer. NOTE: Be sure to install the valve spring with its close-coiled end facing the cylinder head side. Set the ST on valve spring. ST 499718000 VALVE SPRING REMOVER Compress the valve spring and fit the valve spring retainer key. After installing, tap the valve spring retainers lightly with a plastic hammer for better seating.

CYLINDER HEAD

1. Check for cracks or damage. Use liquid penetrant tester on the important informations to check for fissures. Check that there are no marks of gas leaking or water leaking on gasket installing surface.
2. Place the cylinder head on the ST. ST 498267800 CYLINDER HEAD TABLE
3. Measure the warping of the cylinder head surface that mates with cylinder block using a straight edge (A) and thickness gauge (B).

If the warping exceeds the limit, correct the surface by grinding it with a surface grinder.

Warping limit

0.035 mm (0.0014 in)

Grinding limit

0.1 mm (0.004 in)

Standard height of cylinder head

97.5 mm (3.84 in)

Note. Uneven torque for the cylinder head bolts can cause warpage. When reassembling, pay special attention to the torque so as to tighten evenly.

Scheme 491

VALVE SEAT

Inspect the intake and exhaust valve seats, and correct the contact surfaces with a valve seat cutter if they are defective or when valve guides are replaced.

Contacting width W between valve and valve seat

Standard

Intake (A)

0.8 - 1.4 mm (0.03 - 0.055 in)

Exhaust (B)

1.2 - 1.8 mm (0.047- 0.071 in)

Scheme 492

Scheme 493

Scheme 494

Scheme 495

1. Check the clearance between valve guide and valve stem. The clearance can be checked by measuring respectively the outer diameter of valve stem with a micrometer and the inner diameter of valve guide with a caliper gauge. Clearance between the valve guide and valve stem: Standard: Intake 0.035 - 0.062 mm (0.0014 - 0.0024 in) Exhaust 0.040 - 0.067 mm (0.0016 - 0.0026 in)
2. If the clearance between the valve guide and valve stem exceeds the standard, replace the valve guide or valve itself, whichever shows greater amount of wear or damage. See the following procedure for valve guide replacement.

Valve guide inner diameter

6.000 - 6.012 mm (0.2362 - 0.2367 in)

Valve stem outer diameters

Intake

5.950 - 5.965 mm (0.2343 - 0.2348 in)

Exhaust

5.945 - 5.960 mm (0.2341 - 0.2346 in)

Scheme 496

Scheme 497

Scheme 498

Scheme 499

Scheme 500

1. Place the cylinder head on ST1 with the combustion chamber upward so that valve guides fit the holes in ST1.
2. Insert the ST2 into valve guide and press it down to remove the valve guide. ST1 498267800 CYLINDER HEAD TABLE ST2 499767200 VALVE GUIDE REMOVER
3. Turn the cylinder head upside down and place the ST as shown in the figure. Intake side ST 499767700 VALVE GUIDE ADJUSTER Exhaust side ST 499767800 VALVE GUIDE ADJUSTER
4. Before installing a new valve guide, make sure that neither scratches nor damages exist on the inner surface of valve guide holes in cylinder head.
5. Put a new valve guide, coated with sufficient oil, in the cylinder head, and insert the ST1 into valve guide. Press in until the valve guide upper end is flush with the upper surface of ST2. ST1 499767200 VALVE GUIDE REMOVER Intake side ST2 499767700 VALVE GUIDE ADJUSTER Exhaust side ST2 499767800 VALVE GUIDE ADJUSTER
6. Check the valve guide protrusion. Valve guide protrusion L: Intake 20.0 - 21.0 mm (0.787 - 0.827 in) Exhaust 16.5 - 17.5 mm (0.650 - 0.689 in)
7. Ream the inside of valve guide using ST. Put the ST in valve guide, and rotate the ST slowly clockwise while pushing it lightly. Bring the ST back while rotating it clockwise. NOTE: Apply engine oil to the ST when reaming. If the inner surface of valve guide is damaged, the edge of ST should be slightly ground with oil stone. If the inner surface of valve guide becomes lustrous and the ST does not chip, use a new ST or remedy the ST. ST 499767400 VALVE GUIDE REAMER
8. After reaming, clean the valve guide to remove chips.
9. Recheck the contact condition between valve and valve seat after replacing the valve guide.

Scheme 501

1. Inspect the flange of valve and valve stem, and replace the valve with a new part if damaged, worn, deformed, or if dimension "H" in the figure is outside of the specified limit. Head edge thickness H: Intake (A) Standard: 0.8 - 1.2 mm (0.03 - 0.047 in) Exhaust (B) Standard: 1.0 - 1.4 mm (0.039 - 0.055 in)
2. Put a small amount of grinding compound on the valve seat surface, and lap the valve and valve seat surface. Replace with a new valve oil seal after lapping.

Note. It is possible to differentiate between the intake valve and the exhaust valve by their overall length.

Valve overall length

Intake

120.6 mm (4.75 in)

Exhaust

121.7 mm (4.79 in)

VALVE SPRING

1. Check the valve springs for damage, free length, and tension. Replace the valve spring if it is not within the standard value presented in the table.
2. To measure the squareness of the valve spring, stand the valve spring on a surface plate and measure its deflection at the top of the valve spring using a try square.

VALVE SPRING SPECIFICATION

Scheme 502

INTAKE AND EXHAUST VALVE OIL SEAL

1. For the following, replace the oil seal with a new part. See the procedure 2) and subsequent for replacement procedures. When the lip is damaged. When the spring is out of the specified position. When readjusting the surfaces of valve and valve seat. When replacing the valve guide.
2. Place the cylinder head on ST1, and use ST2 to press-fit the oil seal.

ST1 498267800 CYLINDER HEAD TABLE

ST2 498857100 VALVE OIL SEAL GUIDE

Note. Apply engine oil to oil seal before press-fitting. When press-fitting the oil seal, do not use a hammer to strike in. The intake valve oil seals and exhaust valve oil seals are distinguished by their colors.

Color of rubber part

Intake [Gray]

Exhaust [Green]

Scheme 503

Note. Before conducting this procedure, drain the engine oil completely.

Scheme 504

Scheme 505

Scheme 506

Scheme 507

Scheme 508

Scheme 509

Scheme 510

Scheme 511

Scheme 512

1. Remove the V-belts. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.
2. Remove the intake manifold. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/fuel-system/#fuel-injection-system-h4so-except-sti) , Intake Manifold.
3. Remove the crank pulley. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Crank Pulley.
4. Remove the timing belt cover. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt Cover.
5. Remove the timing belt. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt.
6. Remove the crank sprocket. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Crank Sprocket.
7. Remove the generator and A/C compressor with their brackets.
8. Remove the cylinder head. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Cylinder Head.
9. Use the ST to lock the crankshaft, and remove the drive plate. (AT model) ST 498497100 CRANKSHAFT STOPPER
10. Remove the clutch disc and cover. (MT model) Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/clutches-manual-hydraulic/#clutch-system-except-sti__removal) , Clutch Disc and Cover.
11. Remove the flywheel. (MT model) Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/clutches-manual-hydraulic/#clutch-system-except-sti) , Flywheel.
12. Remove the oil separator cover.
13. Remove the water by-pass pipe for heater.
14. Remove the water pump. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/cooling-system-mechanical/#engine-cooling-system-h4so-except-sti__removal) , Water Pump.
15. Remove the bolts which secure oil pump to cylinder block. NOTE: When disassembling and checking the oil pump, loosen the relief valve plug before removing the oil pump.
16. Remove the oil pump from cylinder block using a flat tip screwdriver. CAUTION: Be careful not to scratch the mating surface of cylinder block and oil pump.
17. Remove the front oil seal from the oil pump.
18. Remove the oil pan. Set the part so that the cylinder block LH is on the upper side. Remove the bolts which secure oil pan to cylinder block. Insert an oil pan cutter blade between cylinder block-to-oil pan clearance and remove the oil pan. CAUTION: Do not use a screwdriver or similar tools in place of oil pan cutter.
19. Remove the oil strainer.
20. Remove the baffle plate.
21. Remove the oil filter. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/lubrication-system/#engine-lubrication-system-h4so-except-sti) , Engine Oil Filter.
22. Remove the water pipe assembly.
23. Remove the service hole plugs using a hexagon wrench [14 mm].
24. Remove the service hole cover.
25. Rotate the crankshaft to bring #1 and #2 pistons to bottom dead center position, then remove the piston snap ring through service hole of #1 and #2 cylinders.
26. Draw out the piston pin from #1 and #2 pistons using ST. ST 499097700 PISTON PIN REMOVER NOTE: Be careful not to confuse the original combination of piston, piston pin and cylinder.
27. Similarly draw out the piston pins from #3 and #4 pistons.
28. Remove the cylinder block connecting bolt on the RH side.
29. Loosen the cylinder block connecting bolt on the LH side by 2 to 3 turns.
30. Set the part so that the cylinder block LH is on the upper side, and remove the cylinder block connecting bolt.
31. Separate the cylinder block LH and RH. NOTE: When separating the cylinder block, do not allow the connecting rod to fall or damage the cylinder block.
32. Remove the rear oil seal.
33. Remove the crankshaft along with the connecting rods.
34. Remove the crankshaft bearings from cylinder block using a hammer handle. NOTE: Press the crankshaft bearing at the end opposite to locking lip to remove. Be careful not to confuse the crankshaft bearing combination.
35. Remove each piston from the cylinder block using a wooden bar or hammer handle.

Note. Be careful not to confuse the original combination of piston and cylinder.

Scheme 513

Scheme 514

Scheme 515

Scheme 516

Scheme 517

Scheme 518

Scheme 519

Scheme 520

Scheme 521

Scheme 522

Scheme 523

Scheme 524

Scheme 525

Scheme 526

Scheme 527

Scheme 528

Scheme 529

Scheme 530

Scheme 531

Scheme 532

Scheme 533

Scheme 534

Scheme 535

Scheme 536

Scheme 537

Scheme 538

1. Remove oil on the mating surface of cylinder block before installation. Apply a coat of engine oil to the bearing and crankshaft journal.
2. Position the crankshaft and O-ring on cylinder block RH. NOTE: Use new O-rings.
3. Apply liquid gasket to the mating surfaces of cylinder block RH, and position cylinder block LH. NOTE: Install within 5 min. after applying liquid gasket. Do not allow liquid gasket to jut into O-ring grooves, oil passages, bearing grooves, etc. Liquid gasket: THREE BOND 1217G (Part No. K0877Y0100) or equivalent
4. Apply a coat of engine oil to the washer and bolt thread. NOTE: Use a new seal washer.
5. Tighten the 10 mm cylinder block connecting bolts on the LH side (A - D) in alphabetical order. Tightening torque: 10 N.m (1.0 kgf-m, 7.4 ft-lb)
6. Tighten the 10 mm cylinder block connecting bolts on the RH side (E - J) in alphabetical order. Tightening torque: 10 N.m (1.0 kgf-m, 7.4 ft-lb)
7. Tighten the LH side cylinder block connecting bolts (A - D) further in alphabetical order. Tightening torque: 18 N.m (1.8 kgf-m, 13.3 ft-lb)
8. Tighten the RH side cylinder block connecting bolts (E - J) further in alphabetical order. Tightening torque: 18 N.m (1.8 kgf-m, 13.3 ft-lb)
9. Tighten the LH side cylinder block connecting bolts (A - D) further in alphabetical order. (A), (C): Angle tightening Tightening angle: 90° (B), (D): Torque tightening Tightening torque: 40 N.m (4.1 kgf-m, 29.5 ft-lb)
10. Tighten the RH side cylinder block connecting bolts (E - J) further in alphabetical order. Tightening angle: 90°
11. Tighten the 8 mm and 6 mm cylinder block connecting bolts on the LH side (A - H) in alphabetical order. Tightening torque: (A) - (G): 25 N.m (2.5 kgf-m, 18.4 ft-lb) (H): 6.4 N.m (0.7 kgf-m, 4.7 ft-lb)
12. Apply a coat of engine oil to the oil seal periphery and install the rear oil seal using ST1 and ST2. NOTE: Use a new rear oil seal. ST1 499597100 CRANKSHAFT OIL SEAL GUIDE ST2 499587200 CRANKSHAFT OIL SEAL INSTALLER
13. Position the top ring gap at (A) or (B) in the figure.
14. Position the second ring gap at 180° on the reverse side the top ring gap.
15. Position the upper rail gap at (C) in the figure.
16. Align the upper rail spin stopper (E) to the side hole (D) on the piston.
17. Position the expander gap at (F) on the 180° opposite direction of (C) in the figure.
18. Set the lower rail gap at position (G), located 120° clockwise from (C). NOTE: Make sure ring gaps do not face the same direction. Make sure ring gaps are not within the piston skirt area.
19. install the snap ring. Before positioning the piston on the cylinder block, attach the snap ring in the service hole of the cylinder block, and the piston hole on the opposite side. NOTE: Use new snap rings.
20. Install the piston. Tightening torque: N.m (kgf-m, ft-lb) T: 70 (7.1,51.6) Set the parts so that the #1 and #2 cylinders are on the upper side. Using the ST1, turn the crankshaft so that #1 and #2 connecting rods are set at bottom dead center ST1 499987500 CRANKSHAFT SOCKET Apply a coat of engine oil to the pistons and cylinders and insert pistons in their cylinders using ST2. ST2 498747300 PISTON GUIDE NOTE: Face the piston front mark towards the front of the engine.
21. Install the piston pin. Apply a coat of engine oil to ST3. Insert ST3 into the service hole to align piston pin hole with connecting rod small end. ST3 499017100 PISTON PIN GUIDE Apply a coat of engine oil to piston pin, and insert the piston pin into piston and connecting rod through service hole. Install the snap ring. NOTE: Use new snap rings. Apply liquid gasket to the threaded portion of the service hole plug. Liquid gasket: THREE BOND 1105 (Part No. 004403010) or equivalent Install the service hole plug and gasket. NOTE: Use a new gasket. Tightening torque: 70 N.m (7.1 kgf-m, 51.6 ft-lb) Tightening torque: N.m (kgf-m, ft-lb) T1: 6.4 (0.7,4.7) T2: 70 (7.1,51.6) Set the parts so that the #3 and #4 cylinders are on the upper side. Following the same procedures as used for #1 and #2 cylinders, install the pistons and piston pins. Install the service hole cover. NOTE: Use new O-rings. Tightening torque: 6.4 N.m (0.7 kgf-m, 4.7 ft-lb)
22. Install the water pipe assembly. NOTE: Use new O-rings. Tightening torque: 6.4 N.m (0.7 kgf-m, 4.7 ft-lb)
23. Install the baffle plate. Tightening torque: 6.4 N.m (0.7 kgf-m, 4.7 ft-lb)
24. Install the oil strainer. NOTE: Use new O-rings. Tightening torque: 10 N.m (1.0 kgf-m, 7.4 ft-lb)
25. Tighten the oil strainer stay together with the baffle plate. Tightening torque: 6.4 N.m (0.7 kgf-m, 4.7 ft-lb)
26. Apply liquid gasket to the mating surfaces of oil pan, and install the oil pan. NOTE: Install within 5 min. after applying liquid gasket. Liquid gasket: THREE BOND 1217G (Part No. K0877Y0100) or equivalent Tightening torque: 5 N.m (0.5 kgf-m, 3.7 ft-lb)
27. Apply liquid gasket to the mating surfaces of the oil separator cover and the threaded portion of bolt (A) shown in the figure (when reusing the bolt), and then install the oil separator cover. NOTE: Install within 5 min. after applying liquid gasket. Use new oil separator cover. Liquid gasket: Mating surface THREE BOND 1217G (Part No. K0877Y0100) or equivalent (A) bolt thread (when reusing bolts) THREE BOND 1324 (Part No. 004403042) or equivalent Tightening torque: 6.4 N.m (0.7 kgf-m, 4.7 ft-lb)
28. Use the ST to lock the crankshaft, and install the drive plate. (AT model) ST 498497100 CRANKSHAFT STOPPER Tightening torque: 72 N.m (7.3 kgf-m, 53.1 ft-lb)
29. Install the flywheel. (MT model) Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/clutches-manual-hydraulic/#clutch-system-except-sti) , Flywheel.
30. Install the clutch disc and cover. (MT model) Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/clutches-manual-hydraulic/#clutch-system-except-sti__installation) , Clutch Disc and Cover.
31. Install the oil pump. Using the ST, install the front oil seal. ST 499587100 OIL SEAL INSTALLER NOTE: Use a new front oil seal. Apply liquid gasket to the mating surfaces of oil pump. NOTE: Install within 5 min. after applying liquid gasket. Liquid gasket: THREE BOND 1217G (Part No. K0877Y0100) or equivalent Apply a coat of engine oil to the inside of oil seal. install the oil pump to cylinder block. Be careful not to damage the oil seal during installation. NOTE: Make sure the oil seal lip is not folded. Align the flat surface of oil pump's inner rotor with crankshaft before installation. Use new O-rings and oil seals. Do not forget to assemble O-rings. Apply liquid gasket to the three bolts thread shown in figure, (when reusing bolts) Liquid gasket: THREE BOND 1324 (Part No. 004403042) or equivalent Tightening torque: T: 6.4 N.m (0.7 kgf-m, 4.7 ft-lb)
32. Install the water pump and gasket. NOTE: When installing the water pump, tighten bolts in two stages in alphabetical order as shown in the figure. Use a new gasket. Tightening torque: First: 12 N.m (1.2 kgf-m, 8.9 ft-lb) Second: 12 N.m (1.2 kgf-m, 8.9 ft-lb)
33. Install the water by-pass pipe for heater. Tightening torque: 6.4 N.m (0.7 kgf-m, 4.7 ft-lb)
34. Install the oil filter. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/lubrication-system/#engine-lubrication-system-h4so-except-sti) , Engine Oil Filter.
35. Install the cylinder head. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Cylinder Head.
36. Install the generator and A/C compressor with their brackets. Tightening torque: 36 N.m (3.7 kgf-m, 26.6 ft-lb)
37. Install the crank sprocket. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Crank Sprocket.
38. Install the timing belt. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt.
39. Adjust the valve clearance. Refer to «ADJUSTMENT»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti__adjustment) , Valve Clearance.
40. Install the rocker cover. Install the rocker cover gasket to the rocker cover. NOTE: Use a new rocker cover gasket. Temporarily tighten the bolts in alphabetical order shown in the figure, tighten them in two stages. Tightening torque: First 6.4 N.m (0.7 kgf-m, 4.7 ft-lb) Second (only (a) and (b) are tightened) 6.4 N.m (0.7 kgf-m, 4.7 ft-lb) RH side LH side
41. Install the timing belt cover. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt Cover.
42. Install the crank pulley. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Crank Pulley.
43. Install the intake manifold. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/fuel-system/#fuel-injection-system-h4so-except-sti) , Intake Manifold.
44. Install the V-belts. Refer to «INSTALLATION»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.

Scheme 539

1. Remove the connecting rod cap.
2. Remove the connecting rod bearing. NOTE: Keep the removed connecting rods, connecting rod caps and bearings in order so that they are kept in their original combinations/groups, and not mixed together.
3. Remove the piston rings using piston ring expander.
4. Remove the oil ring by hand. NOTE: Arrange the removed piston rings in proper order, to prevent confusion.
5. Remove the snap ring.

Scheme 540

Tightening torque: N.m (kgf-m, ft-lb)

T: 45 (4.6,33.2)

1. Apply engine oil to the surface of the connecting rod bearings, and install the connecting rod bearings on connecting rods and connecting rod caps.
2. Position each connecting rod with the side with a side mark facing forward, and install it.
3. Attach the connecting rod cap, and tighten with connecting rod nut. Make sure the arrow on connecting rod cap faces the front during installation. NOTE: Each connecting rod has its own mating cap. Make sure that they are assembled correctly by checking their matching number. When tightening the connecting rod nuts, apply oil on the threads. Tightening torque: 45 N.m (4.6 kgf-m, 33.2 ft-lb)
4. Install the oil ring upper rail, expander and lower rail by hand.
5. Install the second ring and top ring using piston ring expander.

Note. Assemble so that the piston ring mark "R" faces the top side of the piston.

CYLINDER BLOCK

1. Check for cracks or damage. Use liquid penetrant tester on the important informations to check for fissures. Check that there are no marks of gas leaking or water leaking on gasket installing surface.
2. Check the oil passages for clogging.
3. Inspect the cylinder head surface that mates with cylinder block for warping by using a straight edge, and correct by grinding if necessary.

Warping limit

0.025 mm (0.00098 in)

Grinding limit

0.1 mm (0.004 in)

Standard height of cylinder block

201.0 mm (7.91 in)

Scheme 541

Scheme 542

Scheme 543

1. The cylinder bore size is stamped on the front upper face of the cylinder block. NOTE: Measurement should be performed at a temperature of 20°C (68°F). Standard sized pistons are classified into two grades, "A" and "B". These grades should be used as guide lines in selecting a standard piston. Standard diameter: A: 99.505 - 99.515 mm (3.9175 - 3.9179 in) B: 99.495 - 99.505 mm (3.9171 - 3.9175 in)
2. Measure inner diameter of each cylinder. Measure the inner diameter of each cylinder in both the thrust and piston pin directions at the heights as shown in the figure, using a cylinder bore gauge. NOTE: Measurement should be performed at a temperature of 20°C (68°F). Taper: Standard: 0.015 mm (0.0006 in) Out-of-roundness: Standard: 0.010 mm (0.0004 in)
3. When the piston is to be replaced due to general or cylinder wear, select a suitable sized piston by measuring the piston clearance.
4. Measure outer diameter of each piston. Measure the outer diameter of each piston at the height as shown in the figure. (Thrust direction) NOTE: Measurement should be performed at a temperature of 20°C (68°F). Piston grade point H: 38.2 mm (1.504 in) Piston outer diameter: Standard A: 99.505 - 99.515 mm (3.9175 - 3.9179 in) B: 99.495 - 99.505 mm (3.9171 - 3.9175 in) 0.25 mm (0.0098 in) oversize: 99.745 - 99.765 mm (3.9270 - 3.9277 in) 0.50 mm (0.0197 in) oversize: 99.995 - 100.015 mm (3.9368 - 3.9376 in)
5. Calculate the clearance between cylinder and piston. NOTE: Measurement should be performed at a temperature of 20°C (68°F). Cylinder to piston clearance at 20°C (68°F): Standard: -0.010-0.010 mm (-0.00039-0.00039 in)
6. Boring and honing If any of the measured value of taper, out-of-roundness or cylinder-to-piston clearance is out of standard or if there is any damage on the cylinder wall, rebore it to replace with an oversize piston. CAUTION: When any of the cylinders needs reboring, all other cylinders must be bored at the same time, and replaced with oversize pistons.
7. If the cylinder inner diameter exceeds the limit after boring and honing, replace the cylinder block.

Note. Immediately after reboring, the cylinder diameter may differ from its real diameter due to temperature rise. Thus, when measuring the cylinder diameter, wait until it has cooled to room temperature.

Cylinder inner diameter boring limit

To 100.005 mm (3.9372 in)

Scheme 544

Scheme 545

Scheme 546

1. Check the piston and piston pin for breaks, cracks or wear. Replace if faulty.
2. Check the piston ring groove for wear and damage. Replace if faulty.
3. Make sure that the piston pin can be inserted into the piston pin hole with a thumb at 20°C (68°F). Replace if faulty. Clearance between piston hole and piston pin: Standard: 0.004 - 0.008 mm (0.0002 - 0.0003 in)
4. Check the snap ring installation groove (A) on the piston for burr. If necessary, remove burr from the groove so that the piston pin can lightly move.
5. Check the piston pin snap ring for distortion, cracks and wear.

Scheme 547

Scheme 548

Scheme 549

1. If the piston ring is broken, damaged or worn, or if its tension is insufficient, or when the piston is replaced, replace the piston ring with a new part of the same size as piston. NOTE: The top ring and second ring have the mark to determine the direction for installing. When installing the ring to piston, face marks to the top side. Oil ring consists of the upper rail, expander and lower rail. When installing oil ring on piston, be careful of the direction of each rail.
2. Using the piston, insert the piston ring and oil ring into the cylinder so that they are perpendicular to the cylinder wall, and measure the piston ring gap with a thickness gauge. PISTON RING GAP SPECIFICATION Standard Standard mm (in) Piston ring gap Top ring 0.20 - 0.35 (0.0079 - 0.0138) Second ring 0.37 - 0.52 (0.0146 - 0.0205) Oil ring rail 0.20 - 0.50 (0.0079 - 0.0197)
3. Fit the piston ring straight into the piston ring groove, then measure the clearance between piston ring and piston ring groove with a thickness gauge. NOTE: Before measuring the clearance, clean the piston ring groove and piston ring. RING SPECIFICATION Standard Standard mm (in) Clearance between piston ring and piston ring groove Top ring 0.040 - 0.080 (0.0016 - 0.0031) Second ring 0.030 - 0.070 (0.0012 - 0.0028)

Scheme 550

Scheme 551

Scheme 552

Scheme 553

1. Replace the connecting rod, if the large or small end thrust surface is damaged.
2. Check for bend or twist using a connecting rod aligner. Replace the connecting rod if the bend or twist exceeds the limit. Limit of bend or twist per 100 mm (3.94 in) in length: 0.10 mm (0.0039 in)
3. Install the connecting rod with bearings attached to the crankshaft, and measure the thrust clearance using a thickness gauge. If the thrust clearance exceeds the standard or uneven wear is found, replace the connecting rod. Connecting rod thrust clearance: Standard: 0.070 - 0.330 mm (0.0028 - 0.0130 in)
4. Inspect the connecting rod bearing for scar, peeling, seizure, melting, wear, etc.
5. Measure the oil clearance on each connecting rod bearing using plastigage. If any oil clearance is not within the standard, replace the defective bearing with a new part of standard size or undersize as necessary. Connecting rod oil clearance: Standard: 0.016 - 0.044 mm (0.0006 - 0.0017 in) BEARING SPECIFICATION Unit: mm (in) Bearing Bearing size (Thickness at center) Outer diameter of crank pin Standard 1.492 - 1.501 (0.0587 - 0.0591) 51.984 - 52.000 (2.0466 - 2.0472) 0.03 (0.0012) Undersize 1.510 - 1.513 (0.0594 - 0.0596) 51.954 - 51.970 (2.0454 - 2.0461) 0.05 (0.0020) Undersize 1.520 - 1.523 (0.0598 - 0.0600) 51.934 - 51.950 (2.0446 - 2.0453) 0.25 (0.0098) Undersize 1.620-1.623 (0.0638 - 0.0639) 51.734 - 51.750 (2.0368 - 2.0374)
6. Inspect the bushing at connecting rod small end, and replace with a new part if worn or damaged.
7. Measure the piston pin clearance at connecting rod small end. If the measured value is not within the standard, replace it with a new part. Clearance between piston pin and bushing: Standard: 0 - 0.022 mm (0 - 0.0009 in)
8. The replacement procedure for the connecting rod small end bushing is as follows. Remove the bushing from connecting rod with ST and press. Press the bushing with the ST after applying oil on the periphery of new bushing. ST 499037100 CONNECTING ROD BUSHING REMOVER AND INSTALLER Make two 3 mm (0.12 in) holes in the pressed bushing to match the pre-manufactured holes on the connecting rod, then ream the inside of the bushing. After completion of reaming, clean the bushing to remove chips.

Scheme 554

Scheme 555

Scheme 556

1. Clean the crankshaft completely, and check it for cracks using liquid penetrant tester. If defective, replace the crankshaft.
2. Measure warping of the crankshaft. If it exceeds the limit, correct or replace it. NOTE: If a suitable V-block is not available, using just the #1 and #5 crankshaft bearings on cylinder block, position the crankshaft on cylinder block. Then, measure the crankshaft bend using a dial gauge. Crankshaft bend limit: 0.035 mm (0.0014 in)
3. Inspect the crank journal and crank pin for wear. If they are not within the standard, replace the bearing with a suitable (undersize) one, and replace or grind to correct the crankshaft as necessary. When grinding the crank journal or crank pin, finish them to the specified dimensions according to the undersize bearing to be used. Crank pin Out-of-roundness 0.003 mm (0.0001 in) Cylindricality 0.004 mm (0.0002 in) Grinding limit (dia.) To 51.750 mm (2.0374 in) Crank journal Out-of-roundness 0.005 mm (0.0002 in) Cylindricality 0.006 mm (0.0002 in) Grinding limit (dia.) To 59.758 mm (2.3527 in) CRANK JOURNAL OUTER DIAMETER SPECIFICATION Unit: mm (in) Crank journal outer diameter Crank pin outer diameter #1,#3 #2, #4, #5 Standard Journal O.D. 59.992 - 60.008 (2.3619 - 2.3625) 59.992 - 60.008 (2.3619 - 2.3625) 51.984 - 52.000 (2.0466 - 2.0472) Bearing size (Thickness at center) 1.998 - 2.011 (0.0787 - 0.0792) 2.000 - 2.013 (0.0787 - 0.0793) 1.492 - 1.501 (0.0587 - 0.0591) 0.03 (0.0012) Undersize Journal O.D. 59.962 - 59.978 (2.3607 - 2.3613) 59.962 - 59.978 (2.3607 - 2.3613) 51.954 - 51.970 (2.0454 - 2.0461) Bearing size (Thickness at center) 2.017 - 2.020 (0.0794 - 0.0795) 2.019 - 2.022 (0.0795 - 0.0796) 1.510 - 1.513 (0.0594 - 0.0596) 0.05 (0.0020) Undersize Journal O.D. 59.942 - 59.958 (2.3599 - 2.3605) 59.942 - 59.958 (2.3599 - 2.3605) 51.934 - 51.950 (2.0446 - 2.0453) Bearing size (Thickness at center) 2.027 - 2.030 (0.0798 - 0.0799) 2.029 - 2.032 (0.0799 - 0.0800) 1.520 - 1.523 (0.0598 - 0.0600) 0.25 (0.0098) Undersize Journal O.D. 59.742 - 59.758 (2.3520 - 2.3527) 59.742 - 59.758 (2.3520 - 2.3527) 51.734 - 51.750 (2.0368 - 2.0374) Bearing size (Thickness at center) 2.127 - 2.130 (0.0837 - 0.0839) 2.129 - 2.132 (0.0838 - 0.0839) 1.620 - 1.623 (0.0638 - 0.0639)
4. Use a thickness gauge to measure the thrust clearance of crankshaft at #5 crank journal bearing. If clearance exceeds the standard, replace the bearing. Crankshaft thrust clearance: Standard: 0.030 - 0.115 mm (0.0012 - 0.0045 in)
5. Inspect individual crankshaft bearings for signs of flaking, seizure, melting and wear.
6. Measure the oil clearance on each crankshaft bearing using plastigage. If the measured value is out of standard, replace the defective bearing with an undersize one, and replace or grind to correct the crankshaft as necessary.

Crankshaft oil clearance

Standard

0.010 - 0.030 mm (0.0004 - 0.0012 in)

Scheme 557

1. Disconnect the ground cable from battery.
2. Remove the air intake chamber. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-intake-system-h4so-except-sti) , Air Intake Chamber.
3. Remove the bolt, and disconnect the engine harness connector from the bulkhead harness connector and rear engine hanger.
4. Slide the bulkhead harness connector in the direction of the arrow and remove it from the rear engine hanger.
5. Disconnect the connector from the oil switching solenoid valve.
6. Remove the oil switching solenoid valve.
7. Remove the variable valve lift diagnosis oil pressure switch. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/fuel-system/#fuel-injection-system-h4so-except-sti) , Variable Valve Lift Diagnosis Oil Pressure Switch.
8. Remove the oil temperature sensor. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/fuel-system/#fuel-injection-system-h4so-except-sti) , Oil Temperature Sensor.
9. Remove the oil switching solenoid valve holder from the cylinder head.

Scheme 558

LH SIDE

1. Disconnect the ground cable from battery.
2. Remove the V-belts. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , V-belt.
3. Remove the crank pulley. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Crank Pulley.
4. Remove the timing belt cover. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt Cover.
5. Remove the timing belt. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Timing Belt.
6. Remove the cam sprocket. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/mechanical/#engine-mechanical-h4so-except-sti) , Cam Sprocket.
7. Remove the timing belt cover No. 2 (LH).
8. Disconnect the connector from the oil switching solenoid valve.
9. Remove the oil switching solenoid valve.
10. Remove the variable valve lift diagnosis oil pressure switch. Refer to «REMOVAL»(/subaru/impreza-wrx-sti/gr-2007-2011/remont/fuel-system/#fuel-injection-system-h4so-except-sti) , Variable Valve Lift Diagnosis Oil Pressure Switch.
11. Remove the oil switching solenoid valve holder from the cylinder head.

Scheme 559

RH SIDE

Install in the reverse order of removal.

Note. Use a new gasket. Apply liquid gasket to variable valve lift diagnosis oil pressure switch threads. Install the oil switching solenoid valve to the holder, then install it to the cylinder head.

Tightening torque

T1:8 N.m (0.8 kgf-m, 5.9 ft-lb)

T2:10 N.m (1.0 kgf-m, 7.4 ft-lb)

T3:17 N.m (1.7 kgf-m, 12.5 ft-lb)

T4:18 N.m (1.8 kgf-m, 13.3 ft-lb)

Liquid gasket

THREE BOND 1324 (Part No. 004403042) or equivalent

Scheme 560

Tightening torque

6.4 N.m (0.7 kgf-m, 4.7 ft-lb)

Install in the reverse order of removal.

Note. Use a new gasket. Apply liquid gasket to variable valve lift diagnosis oil pressure switch threads. Install the oil switching solenoid valve to the holder, then install it to the cylinder head.

Tightening torque

T1:8 N.m (0.8 kgf-m, 5.9 ft-lb)

T2:10 N.m (1.0 kgf-m, 7.4 ft-lb)

T3:17 N.m (1.7 kgf-m, 12.5 ft-lb)

Liquid gasket

THREE BOND 1324 (Part No. 004403042) or equivalent

Scheme 561

Refer to "Cylinder Head" for removal and installation procedures of the intake and exhaust valves. Refer to REMOVAL , Cylinder Head. Refer to INSTALLATION , Cylinder Head.

Refer to " CYLINDER BLOCK " for removal and installation procedures of pistons. Refer to REMOVAL , Cylinder Block. Refer to INSTALLATION , Cylinder Block.

Refer to "Cylinder Block" for removal and installation procedures of connecting rod. Refer to REMOVAL , Cylinder Block. Refer to INSTALLATION , Cylinder Block.

Refer to "Cylinder Block" for removal and installation procedures of the crankshaft. Refer to REMOVAL , Cylinder Block. Refer to INSTALLATION , Cylinder Block.

Note. The "RANK" shown in the chart shows the possibilities of the cause of trouble in order from "Very often" to "Rarely".

A - Very often

B - Sometimes

C - Rarely

ENGINE INSPECTION CHART

ENGINE INSPECTION CHART

See also:
• REMOVAL
• READ CURRENT DATA FOR ENGINE (NORMAL MODE)
• BASIC DIAGNOSTIC PROCEDURE
• REMOVAL
• RELEASING OF FUEL PRESSURE
• REMOVAL
• RH SIDE
• LH SIDE
• PROCEDURE
• REMOVAL
• REMOVAL
• REMOVAL
• REMOVAL
• INSTALLATION
• COMPONENT
• INSTALLATION
• INSPECTION
• TIMING BELT
• REMOVAL
• REMOVAL
• REMOVAL
• INSTALLATION
• INSTALLATION
• ADJUSTMENT
• FRONT SIDE BELT
• REMOVAL
• INTAKE AND EXHAUST VALVE OIL SEAL