7.4L v8 - VIN [N] Chevrolet Cab & Chassis C3500

ENGINE IDENTIFICATION

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

Engine is 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 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 (because the engine uses hydraulic valve lifters), perform the following procedures 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. 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

1. Release fuel system pressure. See 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»(/chevrolet/cab-chassis-c3500/1989-2000/remont/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. (Scheme 15) Install gaskets on cylinder heads.
2. Install intake manifold and bolts. Tighten bolts in sequence to specification. (Scheme 16) See «TORQUE SPECIFICATIONS»(/chevrolet/cab-chassis-c3500/1989-2000/remont/mechanical/#74l-v8-vin-n__torque-specifications). To complete installation, reverse removal procedure. Fill cooling system. Set ignition timing to specification. See «IGNITION TIMING»(/chevrolet/cab-chassis-c3500/1989-2000/remont/adjustments/#engine-controls-adjustments-gasoline) in ON-VEHICLE ADJUSTMENTS - GASOLINE 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 bolts to specification. See TORQUE SPECIFICATIONS. Bend lock tabs (if equipped). To complete installation, reverse removal procedure.

CYLINDER HEAD

Note. The exhaust valve push rods are longer than intake valve push rods.

1. Release fuel system pressure. See FUEL PRESSURE RELEASE. Remove intake manifold. See INTAKE MANIFOLD.
2. Remove exhaust manifold. See EXHAUST MANIFOLD. 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 head bolts in sequence to specification. (Scheme 17) See 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 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 and tighten to specification. See «TORQUE SPECIFICATIONS»(/chevrolet/cab-chassis-c3500/1989-2000/remont/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, ensuring timing marks on sprockets are aligned. (Scheme 18)
2. Install and tighten camshaft sprocket bolts to specification. See «TORQUE SPECIFICATIONS»(/chevrolet/cab-chassis-c3500/1989-2000/remont/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»(/chevrolet/cab-chassis-c3500/1989-2000/remont/mechanical/#74l-v8-vin-n__torque-specifications). To complete installation, reverse removal procedure.

Scheme 18

ROCKER ARM STUDS

Note. Doesn't apply. The cylinder heads on 7.4L engine use rocker arm bolts.

VALVE LIFTERS

Note. The exhaust valve push rods are longer than intake valve push rods.

1. Remove intake manifold. See INTAKE MANIFOLD. 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 valve lifters. See VALVE LIFTERS.
2. Remove timing chain and camshaft sprocket. See TIMING CHAIN & SPROCKETS. 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.
2. If necessary, disconnect the oil level sender from the side of the pan. 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. 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 table under ENGINE SPECIFICATIONS.
2. Measure installed height between cylinder head spring seat (or top of shim, if shimmed) and top of spring shield (top of spring on 7.4L). 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 table and PISTONS, PINS & RINGS 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 rod bearing journal out-of-round, taper and oil clearance. If measurement is not within specification, replace rod bearings and/or machine crankshaft. See CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS table under ENGINE SPECIFICATIONS.
2. Ensure rod side play is within specification. See CONNECTING RODS 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 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. 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 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.

Description

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. The pick-up tube and pump are serviced as an assembly.

Removal & Disassembly

1. Remove oil pan. See 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. Install oil pan.

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

GENERAL ENGINE SPECIFICATIONS

GENERAL ENGINE SPECIFICATIONS

CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS SPECS

CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS SPECS

CONNECTING RODS SPECIFICATIONS

CONNECTING RODS SPECIFICATIONS

PISTONS, PINS & RINGS SPECIFICATIONS

PISTONS, PINS & RINGS SPECIFICATIONS

CYLINDER BLOCK SPECIFICATIONS

CYLINDER BLOCK SPECIFICATIONS

VALVES & VALVE SPRINGS SPECIFICATIONS

VALVES & VALVE SPRINGS SPECIFICATIONS

CYLINDER HEAD SPECIFICATIONS

CYLINDER HEAD SPECIFICATIONS

CAMSHAFT SPECIFICATIONS

CAMSHAFT SPECIFICATIONS

See also:
• ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION
• COMPUTER RELEARN PROCEDURES
• IGNITION TIMING
• FUEL PRESSURE RELEASE
• TORQUE SPECIFICATIONS