REMOVAL & INSTALLATION
Inline Six Cylinder Engines
- Remove the grille. Remove the radiator hoses and remove the radiator.
- Remove the timing gear cover.
- Remove the valve cover and gasket, loosen all the rocket arm nuts, and pivot the rocker arms clear of the pushrods.
- Remove the distributor and the fuel pump.
- Remove the pushrods. Remove the coil and then remove the side cover. Remove the valve lifters.
- Remove the two camshaft thrust plate retaining screws by working through the holes in the camshaft gear.
- Remove the camshaft and gear assembly by pulling it out through the front of the block.
- If either the camshaft or the camshaft gear is being renewed, the gear must be pressed off the camshaft. The replacement parts must be assembled in the same way. When placing the gear on the camshaft, press the gear onto the shaft until it bottoms against the gear spacer ring. The end clearance of the thrust plate should be 0.001-0.005 in. (0.0254-0.127mm).
- Prelube the camshaft lobes with clean engine oil and then install the camshaft assembly in the engine. Be careful not to damage the bearings.
- Turn the crankshaft and the camshaft gears so that the timing marks align. Push the camshaft into position and install and torque the thrust plate bolts to 7 ft. lbs. (9 Nm).
- Check camshaft and crankshaft gear runout with a dial indicator. Camshaft gear runout should not exceed 0.004 in. (0.1016mm) and crankshaft gear runout should not be above 0.003 in. (0.0762mm).
- Using a dial indicator, check the backlash at several points between the camshaft and crankshaft gear teeth. Backlash should be 0.004-0.006 in. (0.10160.152mm).
- Install the timing gear cover. Install the harmonic balancer.
- Install the valve lifters and the pushrods. Install the side cover. Install the coil and the fuel pump.
- Install the distributor and set the timing. Pivot the rocker arms over the pushrods and adjust the valves.
- Install the radiator, hoses and grille.
Gasoline V6 and V8 Engines
- Disconnect the battery.
- Drain and remove the radiator.
- Disconnect the fuel line at the fuel pump. Remove the pump on 1978 and later models.
- Disconnect the throttle cable and the air cleaner.
- Remove the alternator belt, loosen the alternator bolts and move the alternator to one side.
- Remove the power steering pump from its brackets and move it out of the way.
- Remove the air conditioning compressor from its brackets and move the compressor out of the way without disconnecting the lines.
- Disconnect the hoses from the water pump.
- Disconnect the electrical and vacuum connections.
- Mark the distributor as to location in the block. Remove the distributor.
- Raise the car and drain the oil pan.
- Remove the exhaust crossover pipe and starter motor.
- Disconnect the exhaust pipe at the manifold.
- Remove the harmonic balancer and pulley.
- Support the engine and remove the front motor mounts.
- Remove the flywheel inspection cover.
- Remove the engine oil pan.
- Support the engine by placing wooden blocks between the exhaust manifolds and the front crossmember.
- Remove the engine front cover.
- Remove the valve covers.
- Remove the intake manifold, oil filler pipe, and temperature sending switch.
- Mark the lifters, pushrods, and rocker arms as to location so that they may be installed in the same position. Remove these parts.
- If the car is equipped with air conditioning, discharge the A/C system and remove the condenser.
- Remove the fuel pump eccentric, camshaft gear, oil slinger, and timing chain. Remove the camshaft thrust plate (on front of camshaft) if equipped.
- Carefully remove the camshaft from the engine.
- Inspect the shaft for signs of excessive wear or damage.
- Liberally coat camshaft and bearing with heavy engine oil or engine assembly lubricant and insert the cam into the engine.
- Align the timing marks on the camshaft and crankshaft gears. See Timing Chain Replacement for details.
- Install the distributor using the locating marks made during removal. If any problems are encountered, see Distributor Installation.
To install, reverse the removal procedure but pay attention to the following points:
- Install the timing indicator before installing the power steering pump bracket.
- Install the flywheel inspection cover after installing the starter.
- Replace the engine oil and radiator coolant.
6.2L Diesel Engines
See Figure 1
- Disconnect the battery.
- Jack up the truck and safely support it with jackstands.
- Drain the cooling system, including the block.
- Disconnect the exhaust pipes at the manifolds. Remove the fan shroud.
- Lower the truck.
- Remove the radiator and fan.
- Remove the vacuum pump, and remove the intake manifolds as previously detailed.
- Remove the injection pump and lines as outlined in Fuel System .
Make sure you cap all injection lines to prevent dirt from entering the system, and tag the lines for later installation
- Remove the water pump.
- Remove the injection pump drive gear.
- Scribe a mark aligning the line on the injection pump flange to the front cover.
- Remove the injection pump from the cover.
- Remove the power steering pump and the generator and lay them aside.
- If the truck is equipped with air conditioning, remove the compressor (with the lines attached) and position it out of the way.
- Remove the valve covers.
- Remove the rocker shaft assemblies and pushrods. Place the pushrods in order in a rack (easily by punching holes in a piece of heavy cardboard and numbering the holes) so that they can be installed in correct order.
- Remove the thermostat housing and the crossover from the cylinder heads.
- Remove the cylinder heads as previously detailed, with the exhaust manifolds attached.
- Remove the valve lifter clamps, guide plates and valve lifters. Place these parts in a rack so they can be installed in the correct order.
- Remove the front cover.
- Remove the timing chain assembly.
- Remove the fuel pump.
- Remove the camshaft retainer plate.
- If the truck is equipped with air conditioning, remove the A/C condenser mounting bolts. Have an assistant help in lifting the condenser out of the way.
- Remove the camshaft by carefully sliding it out of the block.
Whenever a new camshaft installed, GM recommends replacing all the valve lifters, as well as the oil filter. The engine oil must be changed. These measures will help ensure proper wear characteristics of the new camshaft.
- Coat the camshaft lobes with Molykote® or an equivalent lube. Liberally tube the camshaft journals with clean engine oil and install the camshaft carefully.
- Install the camshaft retainer plate and torque the bolts to 20 ft. lbs. (27 Nm).
- Install the fuel pump.
- Install the timing chain assembly as previously detailed.
- Install the front cover as previously detailed.
- Install the valve lifters, guide plates and clamps, and rotate the crankshaft as previously outlined so that the lifters are free to travel.
- Install the cylinder heads.
- Install the pushrods in their original order. Install the rocker shaft assemblies, then install the valve covers.
- Install the injection pump to the front cover, making sure the lines on the pump and the scribe line on the front cover are aligned.
- Install the injection pump driven gear, making sure the gears are aligned. Retime the injection pump.
- Install the remaining engine components in the reverse order of removal. Make the necessary adjustments (drive belts, etc.) and refill the cooling system.
Completely clean the camshaft with solvent, paying special attention to cleaning the oil holes. Visually inspect the cam lobes and bearing journals for excessive wear. If a lobe is questionable, have the cam checked at a reputable machine shop. If a journal or lobe is worn, the camshaft must be reground or replaced. Also have the camshaft checked for straightness on a dial indicator.
If a cam journal is worn, there is a good chance that the bushings are worn.