273 commando Build

stroker402 said
318 composite head gasket were used

View attachment 1716330281

Ok, I’m a bit lost (again lol). That failure looks like detonation. Across from the plug, that’s what it looks like.

Did you post pictures of your plugs? Did you say your compression ratio and cam timing? I apologize if you did.

If you are getting oil in the chambers and you are already on the edge of detonation that will send it right into detonation.