I don’t think there is much risk there. A 150 shot usually is considered safe with normally aspirated ring gap. I think since you have run the car 4 years likely some wear in the cylinders occurred giving you more gap and safety margin. I’ve wondered the same question becuase I recently have built two 406 small block chevys. I used a new Dart SHP block for both engines. If you used a old factory GM block I’d guess you will get more cyclinder wear than in a new block just becuase I’d guess they are less heavy duty and cylinders being thinner casting probably move more when you lean on it. I’ve often wanted to install a nitrous kit on mine. I gapped the rings tight like you did. I’ll bet if you got a lot of passes on that build when you disassemble the gaps are bigger now. You probably could go a 250 shot and put car in the nines!

 

SMH ?*♀ Be safe and open the gaps just my 2 cents

 

dart little m block.

 

Should be .035” top, .025” second (and oil rail top) for new rings... minimum, IMO. The second ring will open up as it seats in. Rings are different. A steel top ring should not wear and will stay the same, the second ring will wear in, as it's tapered. .003” face wear will open up the gap about .010”

If your block was honed properly, you should have nearly zero wear and still have visible crosshatch (the RK finish). Cylinder wear won’t be enough to get that top ring where it needs to be.

 

Should be .035” top, .025” second (and oil rail top) for new rings... minimum, IMO. The second ring will open up as it seats in. Rings are different. A steel top ring should not wear and will stay the same, the second ring will wear in, as it's tapered. .003” face wear will open up the gap about .010”

If your block was honed properly, you should have nearly zero wear and still have visible crosshatch (the RK finish). Cylinder wear won’t be enough to get that top ring where it needs to be.

Sorry ............ I said I gapped my motor at .036 ....... But I should have said I set mine at .036 to run 500 or so shot ..... did not mean to say gap the rings at .036 for a 150 shot at all

I wasn't referring to you....LOL
Check out the bold...

 

SAY WHAT ? Ok I’m going back to the turbo section don’t mind me lol

 

Right ?

 

What material are the rings? Brand?

 

Sealed power i believe steel

 

On a 150 shot it maybe ok (ITS TIGHT THO!) ............... but we both know that plate will do better than 150hp ...... so I would pull it apart and gap it for a real shot of Nitrous and be safe!

I'm building a 421 Sbc right now .... top ring gapped at .036" 2nd is at .032" ........... but I plan on mush more than a 150 shot!

150 shot is fun ....... but 250 sounds better to me!

 

Advise to disassemble and gap the rings seems like a lot of work for a 150 shot. My experience with gapping rings wide like advised above was way too much blow by ( on old GM block ). You hopefully already have or will install a vacuume pump and low tension rings to deal with that wide ring gap blow by or you will end up with oil blowing out of every gasket every pass! I did! The problem with wide ring gap for nitrous and the blow by oil leaks is why I decided to gap the rings in my recent builds as tight as ring manufacturer recommended and not to spray. Certainly there is risk on so many levels to the longevity of your engine if your going to spray. If your willing to invest the work I’m sure it will be worth that effort in faster performance. Good luck sincerely.

 

plasma moly coated ductile iron top ring and

downward taper 2nd ring

 

.018 is kind of tight for a 150 shot in my opinion.... But probably doable....
Is this a 1/4 car or 1/8 mile?

Who ever said .035 for a 150 shot ....REALLY... holy shit
I got an ultra motor that sees 500+ worth of Hose and they are gapped at .036 top .050 second.

Damn..... Maybe I'm in left field with the Cows....LOL

 

Sorry ............ I said I gapped my motor at .036 ....... But I should have said I set mine at .036 to run 500 or so shot ..... did not mean to say gap the rings at .036 for a 150 shot at all

 

Anyone know what a stock 1990s ford 302 motor has for ring gaps? I have put over 300hp on many stock blocks, just to use for comparison. Never an issue.

 

1/4 mile car

 

Yes ran that in 1/4 mile

 

Damn, maybe I should rethink mine! 4.600 bore, 300-350 shot, .030" top, .035" bottom, .015" oil....

 

Yep, old thread…….

OP you still around? How did that IS SNS plate workout in this scenario you described? Or did you not do it?