I have looked and looked and I can't find any 307 pistons that do not have the chamfer.(Unless you go to custom pistons like those made by Ross and others). From digging through GM archives it looks like the chamfer costs about .25 in lost compression in a 307. Has anyone actually measured in some way how many cc's that the chamfer adds.(Don't know how it would be done). This was done to reduce HC emisions in the early 70's. By the way,looking inside my 1980 truck 250 at the pistons they are also chamferd also. I have also seen 250 pistons advertised with .85 and.115 dish. How many cc,s are those dishes in the top of 250 pistons? Jay 6155
