[Rx7man]

What ring gaps are correct for various power levels? Do you have to increase the ring gap from stock over lets say 600hp?

 

[Drothgeb]

It’s more of a heat thing. If you don’t plan on on high egt’s, then stockish gaps at 600hp are probably fine. With my build, I was expecting to see 1600 regularly and possibly as high as 2000. So, I set the top ring to .028” and the second ring to .030”.

 

[Rx7man]

My truck sees 14-1500 for short bursts, I try and keep it at 1300 or less for any extended pulls.

I'd have thought the second ring would be a little tighter than the top

 

[Drothgeb]

The thinking on a slightly wider second ring gap, is to help prevent a pressure buildup between the top and second rings that may cause the top ring to lose seal. Maybe do some searching on it and decide if it’s right for you.

 

[Rx7man]

Again, interesting.. though I would think that defeats the purpose of having a second ring at all!

Seems like Mahle had some funky gapped rings at one point.. maybe mine were from the same run and I missed it? In the case of this thread it seems like it was the 2nd ring that's the problem
https://www.cumminsforum.com/forum/94-98-powertrain/1460634-mahle-ring-gap-all-over-place.html

My #2 cylinder is at 390 psi while the other 5 are at 440 +/- 5psi... I'm probably taking the head off tonight (or starting on it).. what's your best SWAG about what my problem is on that cylinder? doesn't leak coolant or pressurize rad, has a lot of blowby when hot, and it's noticeably soggy on power and turbo spool.. burns some oil but not a whole lot, starts and runs alright.


Got a laugh from this on the genuine Cummins page.. If Cummins thinks anything close to "a couple millimeters" of error in ring gap is a problem.. *sigh*