ive found that a gapless ring sucks for nitrous.my machine shop wont even install them in a motor with a big spray kit.if you think about it,in one small area the ring is half as thin so it will break twice as easy.
as far as end gap goes, ive found that the second ring on a big kit nitrous motor must be about the same as the top.the problem with rings with too little gap is not that they break, its that the end gap closes up with the extrme combustion temps nitrous causes and causes scuffing of the cyl walls.in some cases the increased friction and heat will cause the ring to stick and break, or bend the ringland and cause it to stick in the ringland.im gapping a 4.030 @.24 top and .22 at the bottom, i believe.i was getting some scuffing on my walls and kept incresing the gap the same for top and second,i.e. id go from .20 1st and 18 second to .21 and .19,but i was still getting scuffing with the 350 shot.the last motor i put the top and second real close, like .25-.24 or .24-.23 and the scuffing went away!so second ring gap has been a problem for me.again, this car only runs at the strip, and always on a 350+ shot, every pass.
i think E.T. has more to do with it than EGO, at least for me.

 

I always put 2nd gaps larger than the top gaps by a good amount so even with N2O I would drastically increase the 2nd gaps.

 

i was thinking about this last night, dont quote me on my end gaps, i think thats where i set them, but my memory might have failed me. ive got it on my build sheet ill look it up and post the exact gaps.

 

I consider myself to be N2O challenged(only have a 75 shot for the 406 & 150 for the LT1), so I phoned JE when building the LT1. There was a very helpful Tech that even had a second Tech join the conversation when we went into DCR questions. "There is two sets of thought" they said to me. Their way and the other way. lol! I set the second ring .007 wider per their suggestion of .005 to .010 wider. That said, it was suggested that I were never to use gapless rings with anything over 125 shot, if I were to go progressive they have witnessed 250 on the dyno dependably. I am not sure my environment is as stable as the dyno.

In closing, do your homework, work the tune & be sure you are comfortable with the choices you make.....or change them.

-N2O Challenged

 

I have learned that ring gaps toward the upper limit have a negligible cost in hp and have been going bigger and bigger over the years.

Rich