Engine Mechanical 7.4l v8 - VIN [n] GMC Suburban I

ENGINE IDENTIFICATION

MODEL IDENTIFICATION

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

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

VALVE CLEARANCE ADJUSTMENT

Note. Although valve clearance adjustment is not usually required (engine uses hydraulic valve lifters), perform the following procedure after servicing valve train.

Tighten rocker arm bolts to 40 ft. lbs. (54 N.m).

GENERAL PRECAUTION

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. When ignition is turned off, an internal constant bleed in injection unit relieves fuel system pressure. No further pressure relief is required.

Removal & Installation ("C" & "K" Series Pickup, Sierra & Suburban)

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n__fuel-pressure-release) . Disconnect battery. Remove hood. Drain cooling system.
2. Remove air cleaner, accessory drive belt, fan and water pump pulley. Remove radiator and fan shroud. Disconnect heater hoses from engine. Disconnect fuel lines, electrical connectors, vacuum hoses, coolant hoses and control cables as necessary.
3. Remove A/C compressor and power steering pump with hoses attached and position aside (if equipped). Raise and support vehicle. Drain crankcase. Disconnect exhaust pipes from manifolds. Remove starter. Remove flywheel cover. Remove torque converter bolts (A/T).
4. Remove bellhousing bolts and engine mount through-bolts. Lower vehicle. Support transmission. Attach engine hoist. Remove engine. To install, reverse removal procedure. Fill crankcase and cooling system.

Removal

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n__fuel-pressure-release). 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. DO NOT rotate crankshaft while engine is apart. Remove intake manifold bolts, intake manifold and gaskets. (Scheme 15)

Installation

1. Install front and rear intake manifold seals on cylinder block. Install gaskets on cylinder heads. (Scheme 15)
2. Install intake manifold and bolts. Tighten the retaining bolts in sequence to specification. (Scheme 16) See «TORQUE SPECIFICATIONS»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n__torque-specifications). To complete installation, reverse removal procedure. Fill cooling system. Set ignition timing to specification. See «IGNITION TIMING»(/gmc/suburban/i-1992-1999/remont/adjustments/#engine-controls-adjustments-74l__ignition-timing) in ON-VEHICLE ADJUSTMENTS - 7.4L article in ENGINE PERFORMANCE.

Scheme 15

Scheme 16

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

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

CYLINDER HEAD

Note. Exhaust valve push rods are longer than intake valve push rods.

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n__fuel-pressure-release) . Remove intake manifold. See «INTAKE MANIFOLD»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n) .
2. Remove exhaust manifold. See «EXHAUST MANIFOLD»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n) . 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 Sealant (1052080).
2. Install cylinder head with bolts finger-tight. Tighten retaining head bolts in sequence to specification. (Scheme 17) See «TORQUE SPECIFICATIONS»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n__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/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n__valve-clearance-adjustment) under ADJUSTMENTS.

Scheme 17

Remove accessory drive belt(s) and pulley. Remove crankshaft damper bolt. Using Damper Puller/Installer (J-39046), remove crankshaft damper. Pry seal from cover.

1. Coat seal lip with engine oil. Using Seal Installer (J-22102), install NEW seal in front cover with seal lip facing engine. Apply RTV sealant to Woodruff keyway in crankshaft damper.
2. Using Damper Puller/Installer (J-39046), install crankshaft damper. Install crankshaft damper bolt. Tighten to specification. See «TORQUE SPECIFICATIONS»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n__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-39046), remove crankshaft damper.
2. Remove all mounting brackets and coolant hoses attached to water pump. Remove water pump. Loosen or remove oil pan as necessary for removal of front cover. Remove front cover bolts, front cover and gasket.
3. Rotate crankshaft until timing marks on camshaft and crankshaft sprockets are aligned. (Scheme 18) Remove camshaft sprocket and timing chain. To remove crankshaft sprocket, use Sprocket Puller (J-1619).

1. Install Woodruff key in crankshaft (if removed). Using Crankshaft Sprocket Installer (J-22102), install crankshaft sprocket. Install camshaft sprocket and timing chain. Ensure timing marks on sprockets are aligned. (Scheme 18)
2. Install and tighten camshaft sprocket bolts to specification. See «TORQUE SPECIFICATIONS»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n__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. Using Damper Puller/Installer (J-39046), install crankshaft damper. Install crankshaft damper bolt and tighten to specification. See «TORQUE SPECIFICATIONS»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n__torque-specifications). To complete installation, reverse removal procedure.

Scheme 18

ROCKER ARM STUDS

Removal & Installation

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 or (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. NOTE: Cylinder heads use rocker arm bolts.

VALVE LIFTERS

Note. Exhaust valve push rods are longer than intake valve push rods.

1. Remove intake manifold. See «INTAKE MANIFOLD»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n) . Remove valve covers. Loosen all rocker arm nuts and rotate rockers aside.
2. Remove push rods, noting location for reassembly reference. Remove lifters, noting location for reassembly reference.

Coat lifter base or roller (if equipped) and body with High Viscosity Oil/Zinc (12345501). Install lifters in original location. To complete installation, reverse removal procedure.

1. Remove radiator. Discharge A/C system (if equipped) using approved refrigerant recovery/recycling equipment and remove A/C condenser (if equipped) and grille. Remove the valve lifters. See «VALVE LIFTERS»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n__valve-lifters) .
2. Remove the timing chain and the camshaft sprocket. See «TIMING CHAIN & SPROCKETS»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n) . Remove balance shaft gear (if equipped). Remove thrust plate. If necessary, raise engine. Remove camshaft.

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

Remove transmission, clutch (M/T) and flywheel. Pry seal from housing.

1. Lubricate inner and outer diameter of seal with engine oil. Place seal on Seal Installer (J-38841). 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 complete installation, reverse removal procedure.

OIL PAN

1. Disconnect battery. Remove fan shroud bolts. Move shroud rearward. Remove air cleaner and distributor cap. Raise and support vehicle. Drain crankcase. Remove starter (M/T). Remove flywheel cover and oil filter. CAUTION: Disconnect oil pressure tube from side of engine to prevent damage to tube when engine is raised. CAUTION: On some models disconnect oil level sender from side of pan.
2. Disconnect oil pressure line from side of cylinder block. Remove front engine mount through-bolts. Raise and support engine. Remove oil pan bolts, oil pan and gasket.

1. Apply RTV sealant to both sides of oil pan gasket.
2. Install oil pan. Tighten oil pan bolts to specification. See «TORQUE SPECIFICATIONS»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n__torque-specifications) . To complete installation, 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/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n) table under ENGINE SPECIFICATIONS.
2. Measure installed height between cylinder head spring seat (or top of shim, if shimmed) and top of spring. 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. Intake and exhaust valves use lower umbrella 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. If not within specification, ream valve guide and install valves with oversize stems.

Valves

Replace valve if margin is less than .031" (.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 dimple 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/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n) table and «PISTONS, PINS & RINGS»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n) table under ENGINE SPECIFICATIONS.

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. Install rings with mark on ring facing upward. Position ring end gaps around circumference of piston as shown. (Scheme 19)

Scheme 19

Rod Bearings

1. Measure the rod bearing journal out-of-round, taper and the oil clearance. If the measurement is not within the specification, replace the rod bearings and/or machine crankshaft. Refer to «CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n) table under ENGINE SPECIFICATIONS.
2. Ensure rod side play is within specification. See «CONNECTING RODS»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n) table under ENGINE SPECIFICATIONS. NOTE: If rear main bearing cap is removed, replace rear crankshaft oil seal (transmission must be removed to replace seal).

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/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n) table under ENGINE SPECIFICATIONS.
2. Align thrust bearing surfaces, and measure crankshaft end play. See Thrust Bearing.

Thrust Bearing

1. Install main bearing caps (except rear), and tighten cap bolts to specification. See «TORQUE SPECIFICATIONS»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n__torque-specifications) . Apply anaerobic sealant to cap-to-cylinder block mating surfaces. 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/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n) table under ENGINE SPECIFICATIONS.

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.

ENGINE OILING 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.

Crankcase Capacity

See CRANKCASE CAPACITY table.

CRANKCASE CAPACITY (1)

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. Pick-up tube and pump are serviced as an assembly.

Removal & Disassembly

1. Remove oil pan. See «OIL PAN»(/gmc/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n__oil-pan) under REMOVAL & INSTALLATION. Remove oil pump bolt. Remove pump and extension shaft.
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/suburban/i-1992-1999/remont/mechanical/#engine-mechanical-74l-v8-vin-n__torque-specifications) . Install oil pan.

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

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 SPECIFICATIONS

VALVES & VALVE SPRINGS

CYLINDER HEAD SPECIFICATIONS

CYLINDER HEAD

CAMSHAFT SPECIFICATIONS

CAMSHAFT

See also:
• ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION
• COMPUTER RELEARN PROCEDURES
• IGNITION TIMING
• ENGINE IDENTIFICATION CODES
• FUEL PRESSURE RELEASE
• TORQUE SPECIFICATIONS
• VALVE CLEARANCE ADJUSTMENT
• VALVE LIFTERS
• OIL PAN