See Figures 1 and 2
Hydraulic valve lifters which are found in most late-model engines rarely require adjustment, and are not adjusted as part of a normal tune-up. All adjustment procedures concerning them will be found in Engine & Engine Overhaul . Hydraulic valve lifters must be adjusted whenever the rocker arms have been loosened. Proper adjustment will center the pushrods on the lifters and allow the lifters to perform their job of maintaining zero lash.
SOLID LIFTERS (1964-71)
Before adjusting solid lifters, thoroughly warm the engine. The solid lifters are generally found on older vehicles and on certain high-performance engines.
- Set the parking brake and block the drive wheels, then start and run the engine until it reaches normal operating temperature.
- Remove the valve covers retainers, then remove the covers and gaskets by tapping the end of the cover rearward to break the seal. Do not attempt to pry the cover off.
Until you are thoroughly familiar with the technique, it may take some time to adjust the valves. It is likely that while you are adjusting the valve, some oil will drip onto the exhaust manifold and smoke causing a highly unpleasant working condition. This may be avoided using an extra set of valve covers which can be purchased from a junk yard for only a few dollars. The tops may be cut off the extra covers and they may be temporarily installed on the cylinder heads. The walls of the these covers will keep oil from spilling on the manifolds, while the open tops will allow access to the rocker arm nuts for lash adjustment.
- If possible, avoid being splashed with hot oil using oil deflector clips. Place one at each oil hole in the rocker arm.
- Measure between the rocker arm and the valve stem with a flat feeler gauge, then adjust the rocker arm stud nut until clearance agrees with the specification in the chart. If you are using the modified valve covers for oil control, it may be necessary to make additional modifications in the covers to allow access with the feeler gauge.
- After adjusting all the valves, stop the engine. If you are using the modified valve covers, remove them from the cylinder heads.
- Clean the gasket surfaces, then install the valve covers using new gaskets.
These are initial adjustments usually required after assembling an engine or performing a valve job. They should be followed up by an adjustment with the engine running as described above.
- Set the engine to the No. 1 firing position (No. 1 TDC). This can be accomplished by removing the No. 1 spark plug and feeling for compression and the engine is slowly turned or by removing the valve cover and watching the valves for the No. 1 cylinder as the engine is turned. If the valves move while the timing notch approaches the 0 mark on the timing scale, then the engine crankshaft is 360 degrees away from No. 1 TDC. If the valves do not move while the notch approaches the 0 mark, then the No. 1 cylinder is at TDC.
- Adjust the clearance between the valve stems and the rocker arms using a feeler gauge. Check the chart for the proper clearance. Adjust the following valves in the No. 1 firing position: Intake No. 2, 7, Exhaust No. 4, 8.
- Turn the crankshaft 1 / 2 revolution clockwise. Adjust the following valves: Intake no. 1,8, Exhaust No. 3, 6.
- Turn the crankshaft 1 / 2 revolution clockwise to the top of the No. 1 piston's exhaust stroke (this is TDC for No. 6 cylinder on V8 engines). Adjust the following valves in this position: Intake No. 3, 4, Exhaust No. 5, 7.
- Turn the crankshaft 1 / 2 revolution clockwise. Adjust the following valves: Intake No. 5, 6, Exhaust No. 1, 2.
- Run the engine until the normal operating temperature is reached. Reset all clearances, using the procedures listed above under Engine Running.
HYDRAULIC LIFTERS-1972 AND LATER
All models, with the exception of those few already discussed, use a hydraulic tappet system with adjustable rocker mounting nuts to obtain zero lash. No periodic adjustment is necessary.