To check the cam, pull the lifters out one at time and look at the bottom surface that rides on the cam itself. If you see a circular wear pattern then its good. If you see a straight line running across the wear surface its going bad. This tells you whether the lifters are spinning as they are intended. Keep the lifters in order as you remove them, if you intend to reuse the cam and lifter as a set. The lifters can be dis-assembled and cleaned.