I just built my mahle piston motor with very large gaps. .028 on the top/second ring. I was thinking they sent wrong rings but was impatient to wait for another set. Then I measured the old motor at .025 and they had great seal. So I decided to run the .028 for experiment sake. Results are the rings seal is fantastic with no blowby. I have read about experiment of running large gaps on second ring with possitive results.

I know from this I will never run tight gaps. I wish I knew exactly how much expansion there is for our apps. If the gap closes after the ring expands you are in trouble.