looking for a set of heads casting number 64, you got any Terryby Terry Kiser - Pontiac GTO Forum
I had the same problem and I found out that the front and rear carbs were opening do to weak springs, I removed the front and rear carbs, blocked the opennings and ran the car, thats how I found the problem. This may not be your problem or not. it can also be in the dist. weak or worn fly weight or springs.by Terry Kiser - Pontiac GTO Forum