Is there a point when heads can be milled no more?? I'm in the process of looking for a set of heads and I'm seeing where most factory 243's are at 64cc. Say, for instance, I buy a set of 59cc heads; does this affect the life of the heads?? If I take them off in a couple years and have them decked, is it still possible??

 

You can mill until you hit the valve seats, but you're significantly weakening the deck by removing so much material.