I was concerned about the orientation of each piston and the slot. 2 pistons on each side had a burn hole through to the top ring. The only other odd thing I found was in the chambers of the head, on each head I found a square bump in the chamber casting right in front of the spark plug hole on the thrust side in all 4 pistons. Is it possible the bump impeded the flame travel and over the miles it burned a hole through all the pistons where the chamber had these bumps. The other 4 chambers did not have these bumps.