Derek, since this is kind of a generic thread I thought I'd post this here. Recently we discussed the "bumpy' port on the Irvine .40. I've been working on a Webra .91 ringed engine and discovered it too has a bumpy port, its hidden by the cooling fins, it also has the matching port in the piston. This engine is getting a new Frank Bowman ring maybe tomorrow and will become a Diesel.