for the people making north of ~600 wheel are you having headgasket issues? If so when did you find that o-ringing the head was necessary?

 

We've made upward of 650whp without o-rings. A cometic with properly installed studs and the proper surface finish will hold up on nearly anything but an all-out race engine. A cometic on a factory deck surface, however, will have the propensity to fail prematurely. Gasket failures can normally be traced back to either the wrong surface finish or a poor tune.