alrighty, i currently have a b18c1 with CTR pistons that are .25 over. the bore sizes are measured in millimeters. my question is: the b18c1 stock bore is an 81 mm, is my current bore 81.5 in millimeters? i'm looking into swapping for higher comp pistons like 12:1. any help would be appreciative.

 

if you are using a gsr head. your compression should be at 12:1 already.