REMOVAL & INSTALLATION
Inline Six Cylinder Engines
See Figure 1
- Remove the rocker arm cover.
- Loosen the rocker arm until you can rotate it away from the pushrod, giving clearance to the top of the pushrod.
- Remove the pushrod. If you are replacing all of the lifters, it is wise to make a pushrod holder as mentioned under Cylinder Head Removal. This will help keep the pushrods in order, as they MUST go back in their original positions.
- Remove the pushrod covers on the side of the block.
- Remove the lifter(s). A Hydraulic lifter removal tool (GM part #J-3049 or equivalent) is available at dealers and most parts stores, and is quite handy for this procedure.
- Before installing new lifters, all sealer coating must be removed from the inside. This can be done with kerosene or carburetor cleaning solvent. Also, the new lifters must be primed before installation, as dry lifters will seize when the engine is started. Submerge the lifters in clean engine oil and work the lifter plunger up and down.
- Install the lifter(s) and pushrod(s) into the cylinder block in their original positions.
- Pivot the rocker arm back into its original position. With the lifter on the base circle of the camshaft (valve closed), tighten the rocker arm nut to 20 ft. lbs. (27 Nm). Do not over torque. You will have to rotate the crankshaft to do the individual valves.
- Replace the pushrod covers using new gaskets. Replace the rocker arm cover, using a new gasket or sealer.
Gasoline V6 and V8 Engines
See Figures 2 and 3
Valve lifters and pushrods should be kept in order so they can be reinstalled in their original position. Some engines will have both standard size and 0.010 in. (0.254mm) oversize valve lifters as original equipment. The oversize lifters are etched with an O on their sides. The cylinder block will also be marked with an O if the oversize lifter is used.
- Remove the intake manifold and gasket.
- Remove the valve covers, rocker arm assemblies and pushrods.
- If the lifters are coated with varnish, apply carburetor cleaning solvent to the lifter body. The solvent should dissolve the varnish in about 10 minutes.
- Remove the lifters. Remove the lifter retainer guide bolts, and remove the guides. A special tool for removing lifters is available, and is helpful for this procedure.
- New lifter MUST be primed before installation, as dry lifters will seize when the engine is started. Submerge the lifters in clean engine oil and work the lifter plunger up and down.
- Install the lifters and pushrods into the cylinder block in their original order. Install the lifter retainer guide.
- Install the intake manifold gaskets and manifold.
- Position the rocker arms, (rocker arms and balls on the V6) pivots and bolts on the cylinder head.
- Install the valve covers, connect the spark plug wires and install the air cleaner.
6.2L Diesel Engine
See Figures 4 and 5
- Remove the valve covers as previously detailed.
- Remove the rocker shaft assemblies.
- Remove the cylinder head(s).
- Remove the guide clamps and guide plates. It may be necessary to use mechanical fingers to remove the guide plates.
- Using GM tool #J-29834 or another suitable lifter removal tool and a magnet, remove the lifter(s) through the access in the block.
- Coat the lifters with clean engine oil before installation. If installing new lifters, they bust be primed first by working the lifter plunger while the lifter is submerged in clean kerosene or diesel fuel. Lifters that have not been primed will seize when the engine is started.
- Install the lifters in their original positions in the block. A lifter installation tool can be fabricated out of welding rod or similar gauge wire and may help.
- Install the lifter guide plate and guide plate clamp. The crankshaft must be turned 2 full rotations (720°) after assembly of the lifter guide plate clamp to insure free movement of the lifters in the guide plates.
- Install the remainder of components in the reverse order of removal.
The pushrods must be installed with their painted ends facing UP.
VALVE LASH ADJUSTMENT
See Figures 6, 7 and 8
All engines described in this guide use hydraulic lifters, which require no periodic adjustment. In the event of cylinder head removal or any operation that requires disturbing the rocker arms, the rocker arms will need a preliminary adjustment.
Normalize the engine temperature by running it for several minutes. Shut the engine off and remove the valve cover(s). After valve cover removal, torque the cylinder heads to specification. The use if oil stopper clips, readily available on the market is recommended to prevent oil splatter when adjusting valve lash. Restart the engine. Valve lash is set with the engine warm and idling.
Turn the rocker arm nut counterclockwise until the rocker arm begins to clatter. Reverse the direction and turn the rocker arm down slowly until the clatter just stops. This is the zero lash position. Turn the nut down an additional 1 / 4 turn and wait ten seconds until the engine runs smoothly. Continue with additional 1 / 4 turns, waiting ten seconds each time, until the nut has been turned down 1 full turn from the zero lash position. This one turn, preload adjustment must be performed to allow the lifter to adjust itself and prevents possible interference between the valves and pistons. Noisy lifters should be cleaned or replaced.1972-86 Models
- Remove the rocker covers and gaskets.
Adjust the valves on the inline six cylinder engines as follows:
- Mark the distributor housing with a piece of chalk at No. 1 and 6 plug wire positions. Remove the distributor cap with the plug wires attached.
Crank the engine until the distributor rotor points to No. 1 cylinder and the points are open. At this point, adjust the following valves:
No. 1-Exhaust and Intake
- Back out the adjusting nut until lash is felt at the pushrod, then turn the adjusting nut in until all lash is removed. This can be determined by checking pushrod end-play while turning the adjusting nut. When all play has been removed, turn the adjusting nut in 1 full turn.
Crank the engine until the distributor rotor points to No. 6 cylinder and the points are open. The following valves can be adjusted:
Adjust the valves on V6 and V8 engines as follows:
- Crank the engine until the mark on the damper aligns with the TDC or 0° mark on the timing tab and the engine is in No. 1 firing position. This can be determined by placing the fingers on the No. 1 cylinder valves as the marks align. If the valves do not move, it is in No. 1 firing position. If the valves move, it is in No. 6 firing position (No. 4 on the V6) and the crankshaft should be rotated 1 more revolution to the No. 1 firing position.
- The adjustment is made in the same manner as 6 cylinder engines.
- With the engine in No. 1 firing position, the following valves can be adjusted:
- Crank the engine 1 full revolution until the marks are again in alignment. This is No. 6 firing position (No. 4 on the V6). The following valves can now be adjusted:
- Reinstall the rocker arm covers using new gaskets.
- Install the distributor cap and wire assembly.