I prefer to set the valve lash on each valve separately.

My point is placing the cam-follower/tappet/lifter on the middle of the base circle for each valve.
This would not be the situation with the engine set in the "firing TDC" position.

All that is needed is to turn the engine, with the valve cover(s) off, until, say, the exhaust valve is at maximum lift.
From there, the engine should be turned exactly one complete turn and there the exhaust valve lash should be adjusted.

Repeat the same procedure, for adjusting the intake valve.


It is possible for the camshaft to be badly ground, so its axis and the cam's base circle are not concentric, causing an incorrect valve lash, if both valves are set at the same time.