I have gone 11.35 with speedmaster as cast heads running out of gear around 1100'. It was in a 11.5 comp 414 cu/in with a .590 purple shaft and 1 5/8 header's, 4.56 gears and a 28 tall tire. I bought them bare and just hand lapped the valves, no valve job. The converter was bought used and not built for mt combo. Same engine with trick flow heads and 1 7/8 header's and a converter/trans I got from pittsburghracer went 10.75 still running out of gear. I had a new converter built by PTC to try this year.