After bringing in a head to fix some compression issues, the machinist told me that the aluminum was too weak to continue to use the head. They stated that:
1. One of the head bolt washers appears to have dented (embedded into) the aluminum when installed. (I am super careful on torques when installing these)
2. The head failed some sort of "drop test" where an object is bounced off of the head to see how high it bounces.
So obviously my questions are;
2. If, "Yes, really!", what causes this? Assuming overheating.