A few unanswered questions (but maybe I missed them?). Are there any signs that this engine was rebuilt? Original bore and pistons? If it was bored then maybe that's why no cylinder ridge? If it was rebuilt then it's as said incorrect ring end gap or rings broken during install? What's the end gap look like or measure on non-broken rings? Is it just one cylinder (I guess I need to re-read that) with A broken ring, but the title of this thread reads rings How about defective or poor quality piston rings ?