I have a 95 Z28 LT1, car had a bolt broken off in the head when I bought it but was sealed by the gasket. I put headers on the car and the new gasket wouldn't seal, I tried alot of things to fix this but none worked. So today I pulled the head off. (pics later) I got it off and looked to see if the bolt would be pretty easy to get out, then checked my valves, well the exhaust valve for the one that was leaking is white as can be. All the other valves look great, should I replace this one valve or go ahead and do them all?