Rudimentary valve clearance question.

Johnny,you are going about it all in the wrong way.Its true you only have some 350-375 lift on the valve when the piston is at TDC,but your valve is not open at TDC to the full lift.A stock piston and head can handle a 500+ cam with out really looking at it.What you need to do is have a .100 clearance on the intake and about 120 on the exhaust for the valves to not hit the pistons,BUT,this is done with the motor and valve gear installed and set and turning over,and being checked at its valve timing.There is a relation ship between the valve and piston position,when the piston is at TDC,one of two things is happening,its either finishing the exhuast stroke,and stating to open the intake,with the exhaust valve slightly open,or its starting the power stroke down,so the valves have very little lift.When the piston is about a inch down in the bore the valve willbe fully open then,and not at TDC.The Valvles open and close with the cam timing and the piston position.If you need more help,email me your number and i will explain,Mrmopartech