Many liner designs; different angles on tops & sides of windows; different aluminum & brass materials; different lip sizes & thicknesses; different window shapes; different window geometries; different number of windows; many different timings; many different tapers; & many different fits have been tested before arriving at the final design. This does not mean that there is nothing better! The final setup uses ABC technology; a .100 thick liner wall; a full head dia .200 thick lip & eight, 8-32 head bolts passing through the liner lip; which mechanically fastens the liner lip to the crankcase. In fact, the liner lip, the crankcase, the head button & the head, are all the same diameter. These features, when applied to ABC or AAC setups, prevented liner blow out at the top; keep the liner round at the top & stablized the liner at the top when heated during running conditions. Upper liner cooling was also greatly improved with this liner lip design, which allowed very high compression ratio's to be used. All of these things increased the engines HP a significant amount.
