Here's a picture with the head removed. It looks like a couple of pieces of metal were shoved up from below. If they were above the piston rings, they would have gone up higher, I think. The gouges go all the way down to the bottom of the cylinder.

Tomorrow I'm going to take the back plate off again and look closer at the piston skirt and the bearings.

Jim

WARNING: Have small children leave the room before viewing this picture! It is an ugly scene!