Re: Small bubbles at spark plug thread
I had a cylinder head with a crack in the plug threads. You couldn't see it until it turned black with oil/exhaust residue. It was a new head too and the symptoms were oil seeping from the plug threads. I never saw bubbles but I'd check the head very closely if I were you. Compression loss would be minimal but it does make for an ugly engine.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"