2.8l v6 - VIN [r] GMC Cab & Chassis R2500

ENGINE 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 identification number is stamped on a machined pad on front of cylinder block to the rear of engine front cover. The Vehicle Identification Number (VIN) is located on left side of dash panel at base of windshield. The eighth character of the (VIN) denotes engine type.

ENGINE IDENTIFICATION CODES

Valve Arrangement

Left Bank - E-I-I-E-I-E (Front-to-rear).

Right Bank - E-I-E-I-I-E (Front-to-rear).

1. Rotate crankshaft to bring No. 1 piston to TDC of compression stroke. Both No. 1 valves will be closed. Back off adjusting nut until lash (play) is felt at push rod. (Scheme 23)
2. Tighten nut until all lash is removed. Tighten adjusting nut an additional 1 1/2 turns. Adjust valves using sequence listed in VALVE CLEARANCE ADJUSTMENT table.
3. Rotate crankshaft 360 degrees to bring No. 4 piston to TDC of compression stroke. Adjust remaining valves and replace rocker arm covers.

VALVE CLEARANCE ADJUSTMENT

Scheme 19

TROUBLE SHOOTING

Note. To trouble shoot engine mechanical components, see appropriate table in TROUBLE SHOOTING article in GENERAL INFORMATION.

2WD

1. Disconnect battery. Remove hood and air cleaner. Drain cooling system. Remove radiator hoses, transmission cooler lines and upper fan shroud. Remove radiator and fan and heater hoses. Label and disconnect all vacuum hoses at engine. Disconnect throttle and cruise control cables.
2. Disconnect ground wires and cables, main feed wires and any necessary wiring at firewall. Remove distributor cap. Raise vehicle. Disconnect exhaust pipe at converter and both manifolds. Remove strut rods, flywheel inspection cover and torque converter bolts.
3. Remove converter hanger at exhaust pipe and rear shield. Disconnect fuel lines and hoses. Remove two outer air dam bolts and lower fan shroud. Remove left body mount bolts and raise body to remove bellhousing bolts. Lower body and remove motor mount through bolts.
4. Disconnect A/C compressor and power steering pump from engine and set aside (if equipped). Attach lift equipment to engine. Support transmission and carefully remove engine from vehicle.

4WD Models With Automatic Transmission

1. Remove hood. Disconnect battery and underhood light. Raise vehicle. On Blazer models, remove body mounts. On chassis cab models, loosen and remove two front body mounts. On all models, remove front air dam end bolts.
2. Raise body above frame and remove top transmission-to-engine bolts. Lower body to frame. Remove remaining transmission-to-engine bolts. Unbolt and remove No. 2 crossmember. Disconnect exhaust pipe at manifolds. Disconnect converter hanger.
3. Remove front drive shaft at differential and bellhousing cover. Unclip automatic transmission cooler lines at engine. Remove motor mount bolts and flex plate-to-converter bolts. Remove front splash shield and lower fan shroud. Lower vehicle.
4. Drain cooling system. Remove upper fan shroud and radiator hoses. Disconnect automatic transmission cooler lines at radiator. Remove radiator, fan, and air cleaner. Remove A/C compressor and power steering pump from engine and set aside (if equipped).
5. Disconnect fuel lines and hoses. Disconnect vacuum and emission hoses from engine. Disconnect accelerator, throttle valve, and cruise control cables (as equipped). Disconnect engine wiring harness at firewall.
6. Disconnect heater hoses at engine. Disconnect any remaining wiring from engine. Attach hoist to engine and support transmission securely. Remove engine from vehicle.

4WD Models With Manual Transmission

1. Remove hood and air cleaner. Disconnect battery and underhood light. Drain cooling system and remove upper fan shroud. Remove radiator hoses, fan and clutch. Remove radiator.
2. Remove A/C compressor and power steering pump (if equipped). Disconnect fuel lines and hoses. Remove vacuum hoses and heater hoses at engine. Disconnect accelerator and cruise control cables. Disconnect engine wiring harness, main feed wire, and ground strap at firewall.
3. Remove lower fan shroud. Disconnect battery ground at engine. Remove distributor cap and diverter valve. Remove shifter boot and console cover. Remove transfer case shifter, transmission shifter, and transmission shift lever.
4. Raise vehicle. Remove front and rear skid plates. Remove front splash shield. Drain transfer case and transmission. Remove rear drive shaft. Disconnect speedometer cable and front drive shaft. Disconnect shift linkage and vacuum hoses at transfer case.
5. Disconnect parking brake cable. Remove rear mount and converter bracket. Support transfer case. Unbolt transfer case and remove from vehicle. Remove crossmember. Disconnect back-up light wiring and clip. Unbolt slave cylinder and hang to side. Remove transmission. Remove clutch release bearing and flywheel inspection cover.
6. Remove left side body mounting bolts. Lift left side of body and remove bellhousing. Disconnect exhaust at manifolds and converter. Disconnect clutch cross shaft at frame. Remove starter. Remove motor mount bolts. Lower vehicle. Attach lifting device and remove engine.

Removal

1. Remove air cleaner and negative battery cable. Drain cooling system. Disconnect all electrical connectors, vacuum hoses and cables at distributor and TBI unit.
2. Disconnect fuel line(s), distributor cap and ignition wires. Mark position of rotor and remove distributor. Remove rocker arm brackets and rocker arm covers.
3. Remove upper radiator hose and heater hose from engine. Remove A/C drive belt and rotate compressor away from work area. Remove intake manifold and discard gaskets. For cleaning and checking procedures see «ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION»(/gmc/cab-chassis-r2500/1987-1987/remont/engine/#engine-overhaul-procedures-general-information) article.

Scheme 20

1. Clean gasket mating surfaces. Apply 3/16" bead of silicone sealant to front and rear sealing ridges of cylinder block. Remove carbon from exhaust and EGR ports.
2. Install new manifold gaskets and secure with silicone sealant. Cut new side gaskets for installation behind push rods.
3. Install intake manifold. Install and tighten manifold attaching bolts and nuts. (Scheme 20) To complete installation, reverse removal procedure.

Remove negative battery cable. Raise vehicle and separate exhaust pipe from manifold. On left side, remove 4 rear manifold bolts and one nut. Lower vehicle. On both sides, disconnect air diverter valve, hoses and wires. Remove power steering bracket. Remove manifold bolts and manifold.

Installation

To install, clean manifold-to-head mating surfaces and reverse removal procedure.

1. Remove intake manifold and raise vehicle. Disconnect exhaust pipe from manifold and drain cooling system. Remove oil dipstick and tube assembly. Remove alternator with bracket and lower vehicle.
2. Remove rocker arm covers, rocker arms and push rods in sequence for reinstallation in original locations. Remove power steering pump and A/C compressor (if equipped), with mounting brackets. Remove cylinder head bolts and separate cylinder head from engine. For cleaning and checking procedures see «ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION»(/gmc/cab-chassis-r2500/1987-1987/remont/engine/#engine-overhaul-procedures-general-information) article.

1. Clean gasket mating surfaces, head bolts and cylinder block threads. Position head gaskets and cylinder heads on cylinder block. Apply sealant to head bolt threads and install bolts. Tighten bolts in sequence. (Scheme 21)
2. Coat rocker arm balls and rocker arm mating surfaces with assembly lubricant before installing. To complete installation, reverse removal procedure and adjust valves.

Scheme 21

1. Remove rocker arm cover, spark plug, rocker arm and push rod of cylinder to be serviced. Install air hose and adapter to spark plug hole. Apply constant air pressure of 90 psi (6.3 kg/cm 2 ).
2. Using a valve spring compressor, compress valve spring and remove valve retainer locks and oil seal. Release compressor and remove retainer/rotator, oil shield (exhaust only), and valve spring damper. On intake valves, remove Teflon oil seal.

Inspection

Check valve spring tension. Springs (without dampers) should test within 10 lbs. of specification. For complete inspection procedure see ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article.

1. Position valve spring and damper on cylinder head. Install Teflon oil seal on intake valve and oil shield on exhaust valve. Install retainer/rotator on valve spring.
2. Coat "O" ring type seal and valve stem with engine oil. Compress spring and install seal in lower groove of valve stem. Ensure seal is not twisted in groove. Install retainer locks and release compressor. Ensure retainer locks are properly seated in upper groove of valve stem.

VALVE SPRING INSTALLED HEIGHT

Installed height of valve springs should be 1.58" (40 mm). If measurement exceeds specified height, install a .030" (.76 mm) shim at spring seat. For complete measurement procedure, see ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article.

VALVE GUIDES

If valve stem-to-guide clearance exceeds specification, ream valve guide to proper oversize. For complete measurement procedures see ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article.

HYDRAULIC VALVE LIFTERS

If lifters are removed, they must be installed in the original positions. Some engines may have both standard and.010" (.25 mm) oversize valve lifters. Engines with oversize lifters will be marked with a dab of White paint and "0.25 O.S." stamped on lifter boss. Refer to Fig. (Scheme 22). For lifter inspection procedure, refer to ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article.

Scheme 22

Remove negative battery cable and all drive belts. Drain cooling system and remove water pump. Remove A/C compressor and mounting bracket (if equipped). Remove vibration damper. Disconnect lower radiator hose at front cover and heater hose at water pump. Remove front cover with retaining bolts and gasket.

To install, use new gasket and reverse removal procedure. See TORQUE SPECIFICATIONS . Ensure water pump bolts are coated with sealant.

Oil seal may be replaced with front cover installed. Remove vibration damper. Using large screwdriver, pry seal out of cover. Use care not to damage crankshaft sealing area or front cover.

Lubricate and install new seal with open side of seal toward inside of front cover. Use Seal Installer (J-35468) to drive seal into position. Install vibration damper. See TORQUE SPECIFICATIONS .

1. Remove front cover. Rotate crankshaft so No. 4 piston is at TDC of compression stroke. Timing marks on camshaft and crankshaft sprockets should be aligned. No. 1 piston will be at TDC of exhaust stroke. (Scheme 23)
2. Remove camshaft sprocket bolts, sprocket and chain. If camshaft sprocket resists removal, use a soft faced hammer and lightly tap lower area of sprocket. Avoid letting camshaft or crankshaft turn. For inspection procedures see «ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION»(/gmc/cab-chassis-r2500/1987-1987/remont/engine/#engine-overhaul-procedures-general-information) article.

Install timing chain and camshaft sprocket. Timing marks must be aligned. (Scheme 23) Install remaining components in reverse order of removal.

Scheme 23

Drain cooling system. Remove radiator. Remove fuel pump, front cover and intake manifold. Remove rocker arm assemblies, push rods and valve lifters in sequence for installation in original locations. Remove timing chain and sprocket. Carefully remove camshaft.

Intake lobe lift is .231" (5.87 mm) and exhaust lift is .263" (6.67 mm). Replace camshaft and lifters if not within specification. For inspection procedures see ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article.

Lubricate journals with oil and camshaft lobes with assembly lubricant. Carefully install camshaft. Lubricate rocker arm ball and valve contact surface. To complete installation, reverse removal procedure.

OIL PAN

See OIL PAN REMOVAL article.

Remove oil pan, oil pump and cylinder heads. Place piston at lower end of stroke and cover with cloth to collect cuttings. Clean ridge or deposits from cylinder bore. Mark connecting rod and cap for installation in original location and remove. For inspection procedure see ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article.

1. Install rings on piston and position ring gaps. Refer to Fig. (Scheme 24). Apply a light coat of engine oil to piston, rings and cylinder bore. Compress piston rings with ring compressor.
2. Cover rod bolts with protective rubber hose. Install piston with notch (or machined hole) in piston head, toward front of engine. Rod bearing tang slot must be positioned away from camshaft. Install rod caps with bearings and tighten to 39 ft. lbs. (53 N.m).

FITTING PISTONS

Cylinder bore taper and out-of-round must not exceed .004" (.10 mm). If taper or out-of-round are not within limits, rebore cylinders. Replacement pistons are available in standard, .020" (.50 mm) and .040" (1.0 mm) oversizes. When reboring cylinders, all main bearing caps must be installed and tightened. For measurement and installation procedures, see ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article.

FITTING RINGS

Measure ring end gap with a feeler gauge. See PISTONS, PINS, RINGS table for specifications. Check side clearance of compression rings with feeler gauge inserted between ring and ring groove. Install and properly space rings on piston. Oil ring spacer ends must be butted, not overlapped. Note that oil ring spacer anti-rotation tang is inserted into oil hole (or slot) of piston.

Scheme 24

Remove piston compression and oil rings. Using Piston Pin Tool (J-24086), press pin from piston and connecting rod.

Replace piston and pin assembly if not within specification. Use Piston Pin Tool (J-24086) to press piston into place.

CONNECTING ROD BEARING SERVICE

1. Use Plastigage method to check rod bearing clearance. Clean crankshaft journal and bearing seat in rod and cap. Insert bearings in rod and cap and coat with engine oil. Pull piston and rod assembly onto crankshaft and install rod cap.
2. After all rods are installed, check side play. Replacement bearings are available in standard, .0005" (.013 mm) and .0010" (.026 mm) undersizes for use with standard size crankshaft. For complete bearing clearance measurement procedures, see «ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION»(/gmc/cab-chassis-r2500/1987-1987/remont/engine/#engine-overhaul-procedures-general-information) article.

MAIN BEARING SERVICE

1. Use Plastigage method to check bearings. New bearings are available in standard, .006" (.15 mm) and .012" (.30 mm) undersizes. Always replace both upper and lower bearing halves together. For complete bearing clearance measurement procedures, see «ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION»(/gmc/cab-chassis-r2500/1987-1987/remont/engine/#engine-overhaul-procedures-general-information) article.
2. Remove main bearings from cylinder block by inserting bearing remover/installer in crankshaft oil hole. Rotate crankshaft clockwise. If remover/installer is unavailable, use a bent cotter pin.
3. Lubricate journal and bearing. Insert plain end of bearing between crankshaft and notched side of block. With bearing remover/installer in crankshaft oil hole, rotate crankshaft counterclockwise to install bearing.
4. Install lower bearing half into cap and lubricate with engine oil. Install and tighten main bearing cap with arrow pointing toward front of engine.

THRUST BEARING ALIGNMENT

1. Ensure all main bearing caps, except No. 3, are installed and tightened. Tighten No. 3 thrust bearing cap bolts to 11 ft. lbs. (15 N.m).
2. Tap end of crankshaft back and forth to line up main bearing and crankshaft thrust surfaces. Tighten thrust bearing cap. Retighten all main bearing cap bolts, including thrust bearing. Rotate crankshaft to confirm free movement.

CRANKSHAFT END PLAY

Crankshaft end play after aligning thrust bearing should be .002-.008" (.05-.21 mm). For checking procedure, see ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article.

Remove transmission and flexplate. Insert a screwdriver through seal dust lip at an angle. Carefully pry out seal.

1. Apply a light coat of oil to inside diameter of new seal. Install new seal over mandrel of Seal Installer (J-34686) until dust lip bottoms against collar of tool. Install seal installer to crankshaft and tighten attaching screws by hand. Ensure dowel pin of seal installer is aligned with dowel pin hole in crankshaft. Refer to Fig. (Scheme 25).
2. Apply light coat of oil to outside diameter of seal. Install seal into bore using seal installer. To complete installation, reverse removal procedure.

Scheme 25

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

GENERAL ENGINE SPECIFICATIONS

GENERAL ENGINE SPECIFICATIONS

VALVE SPECIFICATIONS

VALVE SPECIFICATIONS

PISTON/PIN/RING SPECIFICATIONS

PISTONS, PINS & RINGS SPECIFICATIONS

BEARING SPECIFICATIONS

MAIN & ROD BEARINGS SPECIFICATIONS

VALVE SPRING SPECIFICATIONS

VALVE SPRINGS SPECIFICATIONS

CAMSHAFT SPECIFICATIONS

CAMSHAFT SPECIFICATIONS

See also:
• ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION
• TORQUE SPECIFICATIONS