piston to valve clearance

vegetable

Active Member
#1
Would I be ok running a .308 cam with 1.2 ratio rockers, .065 milled head and a .032 head gasket? I want to make sure the valves wont be able to hit the piston but since this is my first time doing up a head like this how can i check
 
#2
Is the motor apart? If it is using play dough on the piston top put head on with the gasket snug it up then rotate endine with the valves correctlfy adjusted. then remove the head and check the thickness of the valve indentation at the thinnest with a caliper. You want a minimum of .060 clearance. If the engine is assembled then you can check with a dial indicator setup with the dial indicator tip on the valve retainer and starting at 15 degrees before TDC on the overlap stroke, zero the indicator and rotate endine till 15 degrees after in 3 degree increments, push down on the valve end of the rocker and check that the travel on the dial indicator moves more than .060 for each time you move it. The overlap time is the only time the valve gets near the piston. Duration and LSA are what causes too little V to P. What is your piston to head clearance? To be safe you should have a minimum of .030 and a max of .040. Also the exhaust valve is the one that will hit the piston first as the piston is chasing the closing exhaust and if the exhaust floats bang. DSC00685.JPG
 
Top