adjustment, also called tappet clearance adjustment or rocker adjustment, is critical to
the performance and service life of an engine. If the valve train is too loose (too much
clearance), it can cause valve train noise (tapping or clattering noise from the rocker
striking the valve stems). This can increase part wear and cause part breakage. Valves
that are adjusted too tight (inadequate clearance) may be held open or may not close
completely. This can allow combustion heat to blow over and burn the valve.
reassembling an engine after reconditioning the valves, make sure the adjusting screws are
backed off before rotating the engine. A valve that is too tight could strike the piston
and damage either the piston or the valve, or both. Adjust the valve according to
manufacturers specifications, following the recommended procedure.
On any engine,
after valve adjustments have been made, be sure that the adjustment locks are tight and
that the valve mechanism covers and gaskets are in place and fastened securely to prevent