Setting Valve Clearance using Vacuum Gauge
Good way to wipe out a cam or damage valve gear. The specified lash has a lot to do with the ramp angle of the lobe. Too tight lash will cause the lifter to maintain pressure on the base circle too long and not allow oil to get between the lifter face and the cam. In severe cases the valves may not seat completely and they will overheat and burn. Remember the valves grow in length as they heat up, this may be several thousandths at full throttle. Too loose of lash and parts will beat themselves to death. And it sounds like crap. Cam cards have a specified lash, which should be followed.