just wondering if anyone knows when they say, Designed to be used with stock engines, but has valve relief for high lift, long duration cam. do I need thos cams or I can add the cams later with out changing the piston?

thanks

 

Designed for stock engines, pretty much says it all. Deeper valve reliefs will help avoid valve to piston contact if you were running a camshaft with more lift and duration. So if you add a cam later, you're good to go.