well you need to check all the things i said .sounds like something is hitting . i have used 760 lift roller cams on the street and use 260lbs at the seat and over 650 and never had any studs go bad. if you are using more spring than is like 350 @ at seat and 1010 open all bets are off. the intake is the first valve to get in the way of the piston. the piston will drive it up bend it or bust the piston and more. so you mite want to check and see if them holes are dead .on big cams you need to check piston to valve clearances on all holes