yes sireee dave, i experienced it when i put a 478 lift cam in my motor, ripped all the rocker studs out, what a PITA..... so i ended up going to a newer set of heads that were ported and polished and had rollers and such.... and then the cam was too little because the heads were made to port match my rpm airgap manifold, and then when i got it all together..... i broke a few rods