Im not convinced by ABC engines!! Just doesnt seam to make good engineering sence for maximum performance, at opperating temperature the "blow by" past the piston skirt must rob the engine of power and efficency.
Well you are definitely in the stoneage with that thinking. For high performance racing engines the 'ABC" set-up makes perfect sense. At TDC when detonation takes place the seal between piston and liner is better than a ringed engine. remember the ring has a split in it. Lower down in the stroke there is some clearance between piston and liner thus less friction than with a ringed piston. In any case, at higher rpm the ring cannot keep up with the rpm and bounces up and down in the groove eventually destroying itself.
Very few of the modern ABC type engines use brass for the liner anymore. Nelson has been using an aluminum liner for about ten years or more, now refered to as "AAC"
Ed S