4.3l v6 - Vins [w,z] (including Syclone) GMC Sonoma Syclone

MODEL IDENTIFICATION

MODEL IDENTIFICATION

ENGINE IDENTIFICATION

Note. Information applies to both 1991 and 1992 Syclone and Typhoon.

Note. For engine repair procedures not covered in this article, see ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article in the GENERAL INFORMATION section.

Engine can be identified by eighth character of Vehicle Identification Number (VIN). VIN is stamped on a metal tag on top left end of instrument panel, near windshield. See ENGINE IDENTIFICATION table.

Engine can also be identified by engine identification (ID) number. Number is stamped on front of cylinder block, immediately forward of right cylinder head or on left side of cylinder block, on engine-to-transmission mating flange.

ENGINE IDENTIFICATION

VALVE CLEARANCE ADJUSTMENT (VIN W)

No valve adjustment is necessary. This engine has screw-in rocker arm studs with positive stop shoulders. When the valve train requires service, you simply tighten the rocker arm nuts to 20 ft. lbs. (27 N.m).

VALVE CLEARANCE ADJUSTMENT (VIN Z)

This engine can be equipped with two different rocker arm stud configurations that require different valve lash procedures.

If your engine has screw-in rocker arm studs with positive stop shoulders, no valve adjustment is necessary. When the valve train requires service, you simply tighten the rocker arm nuts to 20 ft. lbs. (27 N.m)

If your engine has pressed-in rocker arm studs, you must follow the valve adjustment procedure outlined below.

1. Rotate engine until No. 1 piston is on TDC of compression stroke. Loosen rocker arm adjusting nut until lash is present.
2. Tighten adjusting nut until lash is removed. Tighten adjusting nut one full turn. Adjust remaining valves (for piston at TDC) as listed in the «VALVE CLEARANCE ADJUSTMENT»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone) table.
3. Rotate crankshaft 360 degrees to bring No. 4 piston to TDC of compression stroke. Adjust remaining valves. See the «VALVE CLEARANCE ADJUSTMENT»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone) table.

VALVE CLEARANCE ADJUSTMENT

TROUBLE SHOOTING

To trouble shoot engine mechanical problems, see ENGINE MECHANICAL in BASIC TROUBLE SHOOTING article in GENERAL INFORMATION.

REMOVAL & INSTALLATION

Note. For reassembly reference, label all electrical connectors, vacuum hoses and fuel lines before removal. Also place mating marks on engine hood and other major assemblies before removal.

FUEL PRESSURE RELEASE

Disconnect battery terminals. Loosen fuel tank cap to relieve tank pressure. Internal constant bleed feature in injection unit relieves fuel system pressure when ignition switch is turned off. No further pressure relief is required.

ENGINE

Removal & Installation (Astro & Safari)

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__fuel-pressure-release) under REMOVAL & INSTALLATION. Disconnect battery. Drain cooling system. Raise and support vehicle.
2. Disconnect exhaust pipes from manifolds. Remove flywheel cover, torque converter bolts (A/T), starter and oil filter. Disconnect engine wiring harness from transmission and frame.
3. Disconnect fuel lines from frame. Disconnect transmission fluid lines and engine oil cooler lines from radiator. Remove lower fan shroud bolts. Remove motor mount through-bolts. Lower vehicle.
4. Remove headlight bezels and grille. Remove lower radiator close-out panel, radiator support braces and radiator cross brace. Remove hood latch mechanism. Discharge A/C system (if equipped) using approved refrigerant recovery/recycling equipment. Remove master cylinder, upper fan shroud, upper radiator core support and radiator.
5. Remove radiator filler panels. Remove engine cover. Disconnect A/C hose from accumulator. Remove A/C compressor and bracket. Remove power steering pump.
6. Disconnect vacuum hoses as necessary. Disconnect engine wiring harness clips from firewall. Remove right kick panel. Disconnect engine wiring harness connector from ESC module. Push connector and harness through firewall. Remove distributor cap and A/C accumulator. Disconnect fuel line from injection unit.
7. Remove transmission dipstick tube. Disconnect heater hose from heater core. Remove horn. Support transmission. Support engine with adjustable jack. Remove bellhousing bolts. Lower engine from vehicle.
8. To install, reverse removal procedure. Fill crankcase and cooling system. Evacuate and charge A/C system.

Removal & Installation (Bravada)

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__fuel-pressure-release) under REMOVAL & INSTALLATION. Disconnect battery. Remove hood. Raise and support vehicle. Drain cooling system and crankcase.
2. Disconnect exhaust pipes from manifolds. Disconnect drive shaft from front differential. Remove starter. Remove flywheel cover and torque converter bolts. Remove engine mount through-bolts. Remove oil filter adapter.
3. Remove strut rod. Remove bellhousing bolts. Disconnect transmission fluid cooler lines from clips. Lower vehicle. Remove air cleaner, upper fan shroud, accessory drive belt and fan/clutch assembly.
4. Remove A/C compressor with hoses attached and position aside (if equipped). Remove radiator. Disconnect power steering hoses from power steering pump. Disconnect fuel lines, electrical connectors, vacuum hoses, coolant hoses and control cables as necessary.
5. Remove alternator. Disconnect spark plug wires from distributor cap. Remove cap. Support transmission. Remove bracket from oil cooler. Attach engine hoist. Remove engine.
6. To install, reverse removal procedure. Fill crankcase and cooling system. Bleed power steering fluid system.

Removal & Installation ("C" & "K" Series)

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__fuel-pressure-release) under REMOVAL & INSTALLATION. Disconnect battery. Remove hood. Remove air cleaner, accessory drive belt, fan and water pump pulley.
2. Drain cooling system. Remove fan shroud and radiator. Disconnect heater hoses from engine. Disconnect fuel lines, electrical connectors, vacuum hoses, coolant hoses and control cables as necessary. Remove A/C compressor and power steering pump with hoses attached and position aside (if equipped).
3. Raise and support vehicle. Drain crankcase. Disconnect exhaust pipes from manifolds. Disconnect strut rods. Remove flywheel cover. Remove starter. Remove torque converter bolts (A/T). Lower vehicle.
4. Support transmission. Attach engine hoist. Remove bellhousing bolts. Remove front engine mount-to-frame bolts. Remove engine. To install, reverse removal procedure. Fill crankcase and cooling system. Evacuate and charge A/C system.

Removal & Installation (Commercial Van)

Note. On Commercial Van, engine and transmission are removed as an assembly through side door.

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__fuel-pressure-release) under REMOVAL & INSTALLATION. Disconnect battery. Drain cooling system. Remove engine cover and floor panel sections.
2. Remove air cleaner, duct and exhaust heat stove pipe. Remove distributor cap and position aside. Disconnect all engine harness electrical connectors and position aside. Disconnect fuel lines from injection unit. Remove fuel line clamps from transmission and position fuel lines aside.
3. Disconnect ground strap from rear end of left cylinder head. Disconnect all transmission harness electrical connectors and position harness aside. Remove transmission shifter (if necessary). Remove upper radiator hose, all accessory drive belts, fan, fan pulley, fan shroud and lower radiator hose.
4. Remove engine oil filler tube. Remove clutch adjuster rod, return spring and pivot arm assembly (M/T). Disconnect exhaust pipes from manifolds. Disconnect battery cable from clamp on cylinder block. Disconnect drive shaft from transmission. Remove transmission mount.
5. Disconnect oil cooler lines from oil filter adapter and oil cooler line clamps from engine. Attach engine hoist. Remove engine mount through-bolts. Remove engine and transmission assembly through side door. To install, reverse removal procedure. Fill crankcase and cooling system.

Removal & Installation ("G" Series)

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__fuel-pressure-release) under REMOVAL & INSTALLATION. Disconnect battery. Drain cooling system. Remove engine cover and air cleaner. Remove power steering fluid reservoir.
2. Remove upper fan shroud, fan, fan pulley, radiator and lower fan shroud. Discharge A/C system (if equipped) using approved refrigerant recovery/recycling equipment. Remove A/C condenser. Remove A/C compressor and brace. Remove alternator. Remove cruise control servo (if equipped).
3. Disconnect fuel lines, electrical connectors, vacuum hoses, coolant hoses and control cables as necessary. Remove injection unit. Remove distributor cap with wires attached. Remove diverter valve assembly and pipe.
4. Remove ignition coil and manifold absolute pressure sensor. Remove upper half of engine oil dipstick tube. Remove engine oil filler tube. Remove headlight bezels, grille and upper radiator support (sheet metal cross panel support).
5. Raise and support vehicle. Drain crankcase. Disconnect exhaust pipes from manifolds. Remove strut rods. Remove flywheel cover. Disconnect oil cooler lines from engine. Remove starter, torque converter bolts (A/T) and engine mount through-bolts.
6. Lower vehicle. Attach engine hoist. Remove bellhousing bolts. Support transmission. Remove engine. To install, reverse removal procedure. Fill crankcase and cooling system. Evacuate and charge A/C system.

Removal & Installation ("S" Series)

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__fuel-pressure-release) under REMOVAL & INSTALLATION. Disconnect battery. Remove hood. Drain cooling system.
2. Disconnect upper radiator hose from radiator. Remove coolant overflow hose and upper fan shroud. Disconnect transmission fluid lines and engine oil cooler lines (if equipped). Remove radiator and fan. Disconnect heater hoses. Remove air cleaner.
3. Disconnect fuel lines, electrical connectors, vacuum hoses, coolant hoses and control cables as necessary. Remove distributor cap. Raise and support vehicle. Disconnect exhaust pipe from converter and manifolds. Remove strut rods and flywheel cover.
4. Remove torque converter bolts (A/T). Remove shield from rear of catalytic converter. Disconnect converter hanger from exhaust pipe. Remove 2 outer air dam bolts. Remove left body mount bolts, raise and support body and remove bellhousing bolts. Lower body.
5. Remove motor mount through-bolts. Lower vehicle. Remove A/C compressor and power steering pump with hoses attached and position aside (if equipped). Attach engine hoist. Support transmission. Remove engine. To install, reverse removal procedure. Fill crankcase and cooling system.

Scheme 16

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__fuel-pressure-release) under REMOVAL & INSTALLATION. Disconnect battery cables and remove battery. Remove hood from vehicle.
2. Remove air cleaner and duct, drain engine coolant radiator and charge air cooler radiator. Remove Turbocharger air inlet elbow, Upper fan shroud and Fan & Pulley nuts. Remove battery tray and vacuum tank.
3. Raise and suitably support vehicle. Remove front tires, wheels and wheelhouse panels. Disconnect muffler(s) and tailpipe from catalytic converter. Remove catalytic converter support bolts, turbocharger outlet pipe bracket and turbocharger outlet pipe nuts. Move outlet pipe and catalytic converter away from the turbocharger.
4. Disconnect electrical connector from charge air cooler radiator temperature sensor and radiator hoses. Remove charge air cooler radiator and exhaust crossover pipe. Lower vehicle.
5. Disconnect transmission cooler lines and upper & lower radiator hoses from radiator. Disconnect engine oil cooler lines and heater & overflow hoses from radiator. Remove radiator.
6. Disconnect oil pipes at filter adapter. Remove power steering pump hoses from steering gear.
7. Remove engine coolant reservoir and A/C compressor from bracket. Move aside. Disconnect charge air cooler clamps, ducts and hoses. Remove charge air cooler from supports.
8. Remove throttle body, throttle body gasket, bolts and cable bracket from upper intake manifold and move aside.
9. Disconnect heater hose from lower intake manifold, electrical connectors and hoses from upper intake manifold. Remove upper in take manifold. (Scheme 16)
10. Disconnect fuel pipes from fuel rail. Disconnect electrical connectors and vacuum lines from engine. Raise and suitably support vehicle.
11. Disconnect rear drive shaft (Support Transmission). Remove transmission crossmember and mount. Disconnect front drive shaft and remove torque converter cover. Disconnect shift linkage from transmission.
12. Remove torque converter bolts. Remove fuel pipes from hoses near transfer case and fuel line bracket from transfer case. Disconnect fuel line, electrical clips and connectors from transmission and transfer case. Remove transfer case and gasket. Disconnect TV cable and transmission cooler lines from transmission. Remove torque converter housing bolts and transmission. Disconnect transmission cooler lines from oil pan.
13. Remove fuel line, oil line and electrical harness clips from cylinder heads. Disconnect starter motor electrical connections and remove starter motor. Remove mount through-bolts and nuts. Lower vehicle.
14. Disconnect electrical connections from oil pressure and knock sensors and ground strap. Install lifting device. Remove Engine. To install, reverse removal procedure. Fill crankcase, cooling system and charge air cooler system.

Removal & Installation ("T" Series, Except Syclone & Typhoon)

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__fuel-pressure-release) under REMOVAL & INSTALLATION. Disconnect battery. Remove hood. Raise and support vehicle.
2. Loosen or remove body mount bolts. Raise and support body. Remove upper bellhousing bolts and front air dam end bolts. Lower body. Remove remaining bellhousing bolts. Remove No. 2 frame crossmember. Disconnect exhaust pipes from manifolds.
3. Disconnect catalytic converter hanger. Remove flywheel cover bolts. Disconnect front drive shaft from differential. Remove flywheel cover. Disconnect transmission cooler lines from engine clips. Remove motor mount bolts.
4. Remove torque converter bolts. Remove front splash shield and lower fan shroud bolts. Lower vehicle. Drain cooling system. Remove upper fan shroud. Disconnect radiator hoses from radiator. Disconnect oil filter pipe from remote oil filter.
5. Remove radiator, fan and air cleaner. Remove A/C compressor and power steering pump with hoses attached and position aside (if equipped). Disconnect fuel lines, electrical connectors, vacuum hoses, coolant hoses and control cables as necessary.
6. Support transmission. Attach engine hoist. Remove engine. To install, reverse removal procedure. Fill crankcase and cooling system.

Removal (VIN W)

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__fuel-pressure-release) under REMOVAL & INSTALLATION. Disconnect battery. Drain cooling system.
2. Disconnect fuel lines, electrical connectors, vacuum hoses, coolant hoses and control cables as necessary. Remove upper intake manifold and gasket. (Scheme 17) Remove alternator bracket, A/C compressor (with hoses attached) and cruise control servo as necessary.
3. Remove distributor cap. Mark distributor rotor in relation to distributor housing. Mark base of distributor housing in relation to lower intake manifold. Remove distributor. Remove electrical connectors, fuel rails and fuel injectors. Remove lower intake manifold bolts, lower intake manifold and gaskets.

Scheme 17

Installation

1. Install gaskets on cylinder heads. Apply a 3/16" bead of RTV silicone sealant to front and rear lower intake manifold-to-cylinder block mounting surfaces. (Scheme 17) Extend bead 1/2" beyond cylinder block-to-cylinder head junction.
2. Install lower intake manifold on cylinder block. Tighten bolts in sequence to specification. (Scheme 18) Install fuel injectors, fuel rails and electrical connectors removed during disassembly.
3. Install distributor, A/C compressor and cruise control servo (if equipped). Install upper intake manifold gasket. Install upper intake manifold and bolts. Tighten retaining bolts in sequence to specification. (Scheme 19) See «TORQUE SPECIFICATIONS»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__torque-specifications).
4. To complete installation, reverse removal procedure. Fill cooling system.

Scheme 18

Scheme 19

Removal (VIN Z, Except Syclone & Typhoon)

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__fuel-pressure-release) under REMOVAL & INSTALLATION. Disconnect battery. Drain cooling system. Remove air cleaner.
2. Disconnect fuel lines, electrical connectors, vacuum hoses, coolant hoses and control cables as necessary. Remove alternator bracket, A/C compressor (with hoses attached), injection unit and cruise control servo as necessary.
3. Remove distributor cap. Mark distributor rotor in relation to distributor housing. Mark base of distributor housing in relation to intake manifold. Remove distributor. Remove intake manifold bolts, intake manifold and gaskets.

1. Install gaskets on cylinder heads. Apply a 3/16" (5 mm) bead of RTV silicone sealant to front and rear intake manifold-to-cylinder block mounting surfaces. (Scheme 20) Extend bead 1/2" (13 mm) beyond cylinder block-to-cylinder head junction.
2. Install intake manifold and bolts. Tighten bolts in sequence to specification. (Scheme 21)or (Scheme 22). See «TORQUE SPECIFICATIONS»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__torque-specifications). To complete installation, reverse removal procedure. Fill cooling system.

Scheme 20

Scheme 21

Scheme 22

Removal (Syclone & Typhoon)

1. Loosen wing bolt at air cleaner and move air cleaner and duct aside. Drain charge air cooler radiator and engine radiator into suitable container.
2. Disconnect negative battery cable.
3. Loosen charge air cooler clamps. Disconnect charge air cooler ducts and hoses.
4. Remove charge air cooler from supports.
5. Remove charge air cooler lateral (center) support.
6. Label electrical connectors and hoses for reassembly reference. Disconnect electrical connectors and hoses as necessary.
7. Remove multi-use bracket from lower intake manifold.
8. Remove throttle body bolts and throttle body. Remove throttle body gasket and discard. Remove throttle cable bracket from upper intake manifold.
9. Remove upper intake manifold bolts and upper intake manifold. Remove upper intake manifold gasket and discard.
10. Disconnect heater hose at lower intake manifold. Disconnect charge air cooler coolant inlet pipe at radiator.
11. Label fuel injector electrical connectors for reassembly reference. Disconnect fuel injector electrical connectors.
12. Disconnect fuel feed and return pipes at fuel rail.
13. Remove fuel rail retaining bolts. Carefully remove fuel rail with injectors attached.
14. Remove rear brace from A/C compressor.
15. Remove turbocharger coolant return line.
16. Disconnect upper radiator hose from lower intake manifold.
17. Disconnect ground strap from lower intake manifold.
18. Disconnect coolant temperature sensor connector.
19. Label spark plug wires at distributor cap for reassembly reference. Disconnect spark plug wires at distributor cap.
20. Remove distributor cap.
21. Mark distributor rotor in relation to distributor housing. Mark base of distributor housing in relation to intake manifold. Remove distributor.
22. Remove lower intake manifold bolts/studs.
23. Remove lower intake manifold. Remove lower intake manifold gaskets and discard.

1. Install gaskets on cylinder heads with port blocking plates facing the rear. Apply a 3/16" (5 mm) bead of RTV silicone sealant to front and rear intake manifold-to-cylinder block mounting surfaces. (Scheme 20) Extend bead 1/2" (13 mm) beyond cylinder block-to-cylinder head junction.
2. Install lower intake manifold and bolts. Tighten lower intake manifold bolts to specification. See «TORQUE SPECIFICATIONS»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__torque-specifications). To complete installation, reverse removal procedure. Tighten upper intake manifold bolts to specification starting with the two middle bolts on each side, then working outward. Fill charge air cooler and charge air cooler radiator. Fill engine radiator.

Removal

Remove heat stove tube. Remove all attached brackets and heat shields. If necessary, remove dip stick tube. Disconnect oxygen sensor electrical connector. Disconnect exhaust pipe from manifold. Remove exhaust manifold bolts and exhaust manifold.

Install manifold. Tighten bolts to specification. See TORQUE SPECIFICATIONS . Bend lock tabs (if equipped). To complete installation, reverse removal procedure.

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__fuel-pressure-release) . Remove intake manifold. Refer to «INTAKE MANIFOLD»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone) .
2. Remove exhaust manifold. See «EXHAUST MANIFOLD»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone) under REMOVAL & INSTALLATION. Remove valve covers. Loosen rocker arm nuts. Rotate rocker arms aside. Remove push rods and mark for reassembly to original locations. Remove cylinder head bolts. Remove cylinder head.

1. Clean gasket surfaces, bolt threads and bolt holes. If using steel head gasket, thinly coat both sides of gasket with sealant. DO NOT apply sealant to composition (steel/asbestos) head gaskets. Position head gasket on cylinder block. Ensure all holes align. Coat head bolt threads with GM(R) Sealant (1052080).
2. Install cylinder head with bolts finger-tight. Tighten head bolts in sequence to specification. (Scheme 25) See «TORQUE SPECIFICATIONS»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__torque-specifications). Lubricate valve tip, rocker arm pivot and push rod socket with Molykote.
3. To complete installation, reverse removal procedure. Adjust valves. See «VALVE CLEARANCE ADJUSTMENT»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__valve-clearance-adjustment-vin-z) under ADJUSTMENTS.

Remove accessory drive belt(s) and pulley. Remove crankshaft damper bolt. Using Damper Puller/Installer (J-23523-E), remove crankshaft damper. Carefully pry seal from cover with screwdriver. DO NOT distort front cover.

1. Coat seal lip with engine oil. Using Seal Installer J-35468) on all others, install new seal in front cover with seal lip facing engine. Apply RTV sealant to Woodruff keyway in crankshaft damper.
2. Install crankshaft damper. Install crankshaft damper bolt and tighten to specification. See «TORQUE SPECIFICATIONS»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__torque-specifications) . To install remaining components, reverse removal procedure.

1. Disconnect battery. Drain cooling system. If necessary, remove radiator shroud. Remove accessory drive belts, fan and pulley. Remove crankshaft damper bolt. Using Damper Puller/Installer (J-23523-E), remove crankshaft damper.
2. Remove all mounting brackets and coolant hoses attached to water pump. Remove water pump. Remove oil pan. See «OIL PAN»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__oil-pan) under REMOVAL & INSTALLATION. Remove front cover and gasket.
3. Rotate crankshaft until timing marks on camshaft and crankshaft sprockets are aligned. (Scheme 23) Remove camshaft sprocket and timing chain. To remove crankshaft sprocket, use Sprocket Puller (J-5825-A).

1. Install Woodruff key in crankshaft (if removed). Using Crankshaft Sprocket Installer (J-5590), install crankshaft sprocket. Install camshaft sprocket and timing chain, ensuring timing marks on sprockets are aligned. (Scheme 23)
2. Install and tighten camshaft sprocket bolts to specification. See «TORQUE SPECIFICATIONS»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__torque-specifications). Install gasket to front cover with gasket sealant. Install front cover and gasket.
3. Apply RTV sealant to Woodruff keyway in crankshaft damper. Install crankshaft damper. Install crankshaft damper bolt and tighten to specification. See «TORQUE SPECIFICATIONS»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__torque-specifications). To install remaining components, reverse removal procedure.

Scheme 23

ROCKER ARM STUDS (PRESS-IN TYPE)

1. Rocker arm studs are pressed into cylinder head. Using Stud Remover (J-5802-01), place remover over stud. Install flat washer and nut. Tighten nut to remove stud from cylinder head.
2. If stud is loose in cylinder head, ream stud bore for oversize stud using Reamer (J-5715) for .003" (.08 mm) oversize stud and (J-6036) for .013" (.33 mm) oversize stud.
3. Coat press-fit area of stud with hypoid axle lubricant. Using Stud Driver (J-6880), drive stud into bore until driver bottoms against cylinder head.

1. Remove intake manifold. See «INTAKE MANIFOLD»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone) . Remove valve covers. Loosen all rocker arm nuts and rotate rockers aside.
2. Remove push rods, noting location for reassembly reference. Remove lifter retainer. On all engines, remove lifters, noting location for reassembly reference.

Coat lifter feet and body with High Viscosity Oil/Zinc (12345501). Install lifters in original location. To install remaining components, reverse removal procedure.

Remove radiator, Discharge A/C system (if equipped) using approved refrigerant recovery/recycling equipment and remove A/C condenser (if equipped) and grille. Remove valve lifters. Refer to VALVE LIFTERS under REMOVAL & INSTALLATION. Remove timing chain and camshaft sprocket. See TIMING CHAIN & SPROCKETS under REMOVAL & INSTALLATION. If necessary, raise engine. Remove camshaft.

Coat camshaft lobes and bearing journals with High Viscosity Oil/Zinc (12345501). Install camshaft. To install remaining components, reverse removal procedure.

Remove transmission, clutch (M/T) and flywheel. Using screwdriver, pry seal from housing. DO NOT scratch crankshaft sealing surface. Note direction of seal lip.

1. Lubricate inner and outer diameter of seal with engine oil. Place seal on Seal Installer (J-35621). Position seal installer against crankshaft.
2. Thread attaching screws into crankshaft flange and tighten with screwdriver. This squares seal with crankshaft. Rotate seal installer handle until it bottoms. Remove seal installer. Install flywheel, clutch (M/T) and transmission.

Disconnect battery. Drain cooling system. Remove all drive belts, coolant hoses and mounting brackets attached to water pump. If necessary, remove fan shroud. Remove fan and pulley. Remove water pump and gaskets.

Install water pump with new gaskets. Tighten water pump bolts to specification. See TORQUE SPECIFICATIONS . To install remaining components, reverse removal procedure.

OIL PAN

Removal (Except "S" & "T" Series)

1. Disconnect battery. Raise and support vehicle. Drain crankcase. Remove exhaust crossover pipe, strut rods, strut rod brackets and flywheel cover.
2. Remove starter. Remove or disconnect engine oil cooler lines and/or transmission fluid lines as necessary. Remove oil pan bolts, oil pan and gasket.

Removal (Bravada, Syclone & Typhoon)

1. Disconnect battery. Remove engine oil dipstick. Raise and support vehicle. Remove accessory drive belt splash shield. Drain crankcase. Remove flywheel cover. Remove front engine mount through-bolts.
2. Raise engine. Support in place with wood blocks. Disconnect oil cooler line. Remove oil filter adapter. Remove pitman arm and idler arm. Remove front differential mount through-bolts. Remove front drive shaft. Roll differential forward. Remove starter. Remove oil pan bolts, oil pan and gasket.

Removal ("S" Series)

Raise and support vehicle. Drain crankcase. Remove engine. See ENGINE under REMOVAL & INSTALLATION. Remove oil pan bolts, oil pan and gasket.

Removal ("T" Series, Except Bravada, Syclone & Typhoon)

1. Disconnect battery. Remove engine oil dipstick and accessory drive belt splash shield. Raise and support vehicle. Drain crankcase. Remove front axle shield and transfer case shield. Remove brake line clips from crossmember.
2. Remove second crossmember. Remove converter hanger bolts and exhaust pipe clamp from converter. Disconnect exhaust pipes from manifolds. Slide exhaust pipe rearward. Disconnect front drive shaft from differential.
3. Remove flywheel cover. Remove starter motor. Remove idler arm-to-frame bolts. Remove differential housing mounting bolts from bracket (right side) and frame (left side).
4. Move differential housing forward. Remove front engine mount through-bolts. Raise and support engine. Remove oil pan bolts, oil pan and gasket.

Installation (All Models)

1. Apply RTV sealant to front cover-to-cylinder block junction and rear main bearing-to-cylinder block junction.
2. Install oil pan. Tighten oil pan bolts to specification. See «TORQUE SPECIFICATIONS»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__torque-specifications) . To install remaining components, reverse removal procedure. Fill crankcase.

Valve Springs

1. Measure valve spring free length, installed height and pressure (tension). Replace valve spring if measurement is not within specification. See «VALVES & VALVE SPRINGS»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone) table under ENGINE SPECIFICATIONS at end of article.
2. Measure installed height between cylinder head spring seat (or top of shim, if shimmed) and top of spring shield. If installed height exceeds specification, install shims as necessary to bring installed height to specification. Ensure installed height is not less than specified.

Valve Stem Oil Seals

1. On intake valve uses upper "O" ring seal and lower umbrella seal; exhaust valve uses upper "O" ring seal.
2. When installing umbrella seal, seat seal against valve guide boss on cylinder head. Coat upper "O" ring seal with engine oil before installation and ensure seal is not twisted when installed.

Valve Guides

Valve guides are part of cylinder head (not replaceable). Measure valve guide oil clearance. See CYLINDER HEAD table under ENGINE SPECIFICATIONS at end of article. If not within specification, ream valve guide and install valves with oversize stems.

Valves

Replace valve if margin is less than 1/32" (.8 mm).

Rocker Arm Assembly

Clean push rods, rocker arms, balls and nuts with solvent and blow dry. Inspect rocker arms and balls at mating surface. Surface should be smooth and free of damage. Inspect push rods for bends or wear. Ensure oil passages are clear.

Piston & Rod Assembly

1. Mark piston in relation to cylinder bore before removal. Piston pin is press-fit in connecting rod. Mark piston in relation to connecting rod before separating components.
2. Replace piston and piston pin as matched set. Install piston in bore with notch on top of piston toward front of engine.

Fitting Pistons

1. Measure piston diameter at 90-degree angle to piston pin, on piston pin center line. Measure cylinder bore diameter 2 1/2" below cylinder block deck. Determine piston clearance.
2. If piston clearance is not within specification, replace piston and/or machine cylinder bore as necessary. See «CYLINDER BLOCK»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone) table and «PISTONS, PINS & RINGS»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone) table under ENGINE SPECIFICATIONS at end of article.

Piston Rings

Measure piston ring end gap and side clearance. If measurement is not within specification, replace piston and/or rings as necessary. See PISTONS, PINS & RINGS table under ENGINE SPECIFICATIONS at end of article. Install rings with mark on ring facing upward. Position ring end gaps around circumference of piston as shown. (Scheme 24)

Scheme 24

Rod Bearings

1. Measure rod bearing journal out-of-round, taper and oil clearance. If measurement is not within specification, replace rod bearings and/or machine crankshaft. Refer to «CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone) table under ENGINE SPECIFICATIONS at end of article.
2. Ensure rod side play is within specification. See «CONNECTING RODS»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone) table under ENGINE SPECIFICATIONS at end of article.

Crankshaft & Main Bearings

1. Mark bearing caps for reassembly. Measure journal diameter, out-of-round, taper and oil clearance. If measurement is not within specification, replace main bearings and/or machine crankshaft. See «CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone) table under ENGINE SPECIFICATIONS at end of article.
2. Align thrust bearing surfaces, and measure crankshaft end play. See Thrust Bearing below.

Note. Distance between rear main bearing thrust faces on some engines is .008" (.20 mm) wider than standard. When replacing rear main bearings on these engines (identified by .008" stamped on crankshaft rear counterweight), use only .008"(.20 mm) wider bearings.

Thrust Bearing

1. Install main bearing caps (except rear), and tighten cap bolts to specification. See «TORQUE SPECIFICATIONS»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__torque-specifications) . Install rear main bearing cap and tighten cap bolts to 10 ft. lbs. (14 N.m).
2. Tap crankshaft rearward then forward to align thrust surfaces. Tighten rear main bearing cap bolts to specification. Measure crankshaft end play at forward thrust surface of rear main bearing cap. See «CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone) table under ENGINE SPECIFICATIONS at end of article.

Cylinder Block

Measure cylinder bore out-of-round and taper. If measurement is not within specification, machine cylinder bore and/or replace piston. See CYLINDER BLOCK table under ENGINE SPECIFICATIONS at end of article.

ENGINE LUBRICATION SYSTEM

Gear-type oil pump delivers full pressure lubrication through full-flow oil filter to main oil gallery. Main oil gallery feeds crankshaft and camshaft bearings through drilled passages in block.

Valve lifter oil gallery feeds valve lifters. From lifters, oil is routed through hollow push rods to upper valve train components. Timing chain and sprockets are lubricated by oil drainage from No. 1 camshaft bearing. Pistons and piston pins are lubricated by oil splash. Non-adjustable oil pressure regulator is located in oil pump body.

Oil Pressure

Measure oil pressure with engine at operating temperature and specified RPM. See OIL PRESSURE SPECIFICATIONS table.

OIL PRESSURE SPECIFICATIONS (1)

OIL PUMP

Note. On all engines, pick-up tube is serviceable, however, DO NOT remove tube from pump body unless tube is damaged.

Removal & Disassembly

1. Remove oil pan. See «OIL PAN»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__oil-pan) under REMOVAL & INSTALLATION. Remove oil pump bolt. Remove pump and extension shaft. On all engines remove pick-up tube (if necessary).
2. Remove pump cover. Mark relationship between gears at a meshing point for reassembly. Remove gears. Remove pressure regulator valve retaining pin. Remove pressure regulator valve and spring.

Inspection

Inspect pump body and cover for cracks or excessive wear. Inspect pump gears for damage or wear. Check drive gear shaft for looseness in pump body. Check pressure regulator valve for fit in bore. Replace entire pump assembly if damaged. Inspect inlet tube and screen assembly for damage.

Reassembly & Installation

1. Install pump gears into pump body with marked gear teeth indexed. If pick-up tube was removed, apply sealant to tube end. Tap tube end into pump using plastic hammer. Reassemble remaining components in reverse order of disassembly.
2. Prime oil pump with engine oil. Install pump and extension shaft, ensuring slot on top of extension shaft engages with drive tang on end of distributor shaft. Tighten oil pump bolt to specification. See «TORQUE SPECIFICATIONS»(/gmc/sonoma-syclone/1991-1992/remont/mechanical/#43l-v6-vins-wz-including-syclone__torque-specifications) . Install oil pan.

ENGINE COOLING

Note. Refer to WATER PUMP under REMOVAL & INSTALLATION in this article.

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

Scheme 25

GENERAL ENGINE SPECIFICATIONS

GENERAL SPECIFICATIONS

CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS SPECIFICATIONS

CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS

CONNECTING RODS SPECIFICATIONS

CONNECTING RODS

PISTONS, PINS & RINGS SPECIFICATIONS

PISTONS, PINS & RINGS

CYLINDER BLOCK SPECIFICATIONS

CYLINDER BLOCK

VALVES & VALVE SPRINGS (Non-Turbo) SPECIFICATIONS

VALVES & VALVE SPRINGS (Non-Turbo)

CYLINDER HEAD SPECIFICATIONS

CYLINDER HEAD

CAMSHAFT SPECIFICATIONS

CAMSHAFT

FLUID CAPACITIES SPECIFICATIONS

FLUID CAPACITIES

See also:
• ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION
• ENGINE MECHANICAL
• ENGINE IDENTIFICATION
• FUEL PRESSURE RELEASE
• TORQUE SPECIFICATIONS
• VALVE CLEARANCE ADJUSTMENT
• OIL PAN
• ENGINE