elgoyoloco

Im at sea level, mostly glamis. I was at 330 mains and it ran perfectly for 7 long and abusive seasons. Rebuilt the topend to freshen it up (.5mm over), but also added the cool head with 21cc domes and advanced the timing +4. It took a couple rides to put a hole in the first piston, then split cases to flush crank of debris and reassembled and uped the jetting. Well I got one break in trip then the next trip same thing, same cylinder (left). I split the cases everytime and replace crank seals to ensure no leaks. The issue is definately compression, but why so high is what is weird.

I just put another hole in a piston for the second time in a row after a full engine rebuild. Stock cylinder .5mm over wiseco pistons, noss cool head with 21cc domes, +4 degrees advanced timing, 370 mains (I went big on the mains after the first piston melt down). Setup should have been fine for pump gas. So I put the head back on and checked compression on the "good" cylinder, 180 psi. How is this possible with 21cc domes? I'm goind to measure the dome cc's I'm thinking they got marked wrong, which has cost me 4 pistons so far. Lesson learned, always check compression after rebuild. Any other ideas what could give me that much compression?