7.4L V8 - VIN [N]: Other GMC Pickup C2500

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

CYLINDER HEAD

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

OIL PAN

VALVE LIFTERS

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

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»(ref-50023-S38407769882001011600000) 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 1/32" (.8 mm).

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»(ref-50023-S33930773162001011600000) table and «PISTONS, PINS & RINGS»(ref-50023-S17684743492001011600000) 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 60)

Scheme 60

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»(ref-50023-S11776468162001011600000) table under ENGINE SPECIFICATIONS.
2. Ensure rod side play is within specification. See «CONNECTING RODS»(ref-50023-S08476057772001011600000) 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»(ref-50023-S11776468162001011600000) 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»(ref-50023-S24466009852001011600000) table. 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»(ref-50023-S11776468162001011600000) 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.

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 together as an assembly.