To many racers and enthusiasts, the concept of valve lash is regarded as a dark art. It seems like some mystery craft that is best left to engine builders and mechanics. Yet, proper valve lash can actually be set by anyone. Not only is it vital to the health of your engine, proper valve lash may also give you an advantage on the track.
Valve lash itself is the mechanical clearance in the valve train from the valve tip to the rocker arm in an engine setup that uses solid/mechanical lifters. Excessive lash will cause a great deal of noise in the engine and wear in the valve train, while lashing too tightly may hang open a valve, thereby not allowing the cylinder to run. Instead of making compression, air will blow through the valve. Thus, proper valve lash is critically important.
To set lash, COMP Cams®
uses the method known as Exhaust Opening, Intake Closing (EOIC). This is just one method, although there are plenty of others. This process works on any pushrod engine.