The valve lash adjustment should be performed only when the engine is hot and running.
- Warm up the engine until it reaches its normal operating temperature.
- Remove the valve cover (two on V8) by withdrawing its securing bolts. Be careful of the hot oil which will splash off the rocker assembly when the cover is removed. It is advisable to use commercially available oil deflector clips on the rocker arms when adjusting the valve lash.
- With the engine idling, loosen the rocker arm nut until the rocker arm begins to clatter.
- Turn the rocker arm nut down slowly until the valve clatter just stops (zero lash position).
- Turn the rocker arm nut down a quarter turn further and pause 10 seconds until the engine runs smoothly. Repeat this procedure three more times, pausing 10 seconds each time, until the rocker arm nut has been turned down one full turn from the zero lash position.
Be sure to perform the one turn preload adjustment slowly as the valve tappet must be allowed to adjust itself. This will prevent the possibility of interference between the valve head and the top of the piston which could result in internal damage and/or bent pushrods.
- Repeat steps three through five to adjust the other valves.
- After all of the valves have been adjusted, stop the engine, remove the oil deflector clips, and replace the valve cover, using a new gasket between the cover and the cylinder head. If much oil was lost during the valve adjustment procedure, check the oil level in the crankcase.