How large of a cam would make fly cutting the piston necessary???

 

Lots of info available, just use the search function. Somewhere in the 234/238 .600/.600 range you should start checking exact clearance and asking the manufacturer what they say the PTVC should be. That is for stock valves and unmilled heads.

Brandon

 

milled heads or stage 2 heads will make you have to flycut sooner.