[MJN]

Simon

I would say that is too tight a clearance for a forged piston. If you have not really leant on the engine you may not have done any real damage to the pistons due to the clearance because they won't have got to max operating temperature.

Also, the photo in your other post looks like a ring clearance issue. Either the ring end gap is too small or could be a ring that has siezed in the ring groove. If that particular cylinder was backfiring, or detonating as you noted then the ring may well have siezed or be pinched in the ring groove due to the ring land being deformed. If it was real bad then the knock may be the wrist pin clearance on that particular piston. It obviously took a bit of a hammering.