Ross #99788 4.2cc dome pistons. 4.00 stroke 4.070 bore .018 out of hole. 65cc heads .040 head gasket=14.02 cr on the summitracing site. Milling off the dome only lowers cr to 13.23. Even going to 72cc heads(x heads) with dome milled off only lowers cr to 12.13. My conclusion:These are race pistons, not for street. Who would want stroker race pistons?? Most anyone building a stroker would buy a complete rotating assembly. I guess I'm going to build my 340, its mostly done already.