Piston Ring End Gap

Thneold standard is .004 per inch of bore. I always rounded up. So on a 4.03 bore that would be .017 on the top ring. One of the newer ideas is to run a wider gap ont eh 2nd ring. It makes sense if you know what the rings do, and how they do it. In this case, I would run a .020 gap on the 2nd ring. That general guide works for forged and cast pistons. It DOES NOT HOLD TRUE FOR HYPEREUTECTICS or many gapless rings. The best bet is to look what the piston manufacturer says to run, and the ring manufacturer says to run, and take the largest gap between those two. That means on some hypers, a top ring gap of .030 or more is right depending on usage. You always want to plan for worst case. And slightly big will only give up some power, not break anything. too tight will break something.