Ring gap formulas

Discussion in 'High Tech for Old Iron' started by Nothingface5384, Sep 27, 2014.

  1. Nothingface5384

    Nothingface5384 Detail To Oil - Car Care

    Just wondering what you guys used

    Piston ring gap formulas

    Bottom ring gap should be 20-30% larger than top ring gap.


    Top rings

    NA gap = .004" per inch of bore diameter

    Oval track = .0045" per inch of bore diameter

    N20 = .005" per inch of bore diameter

    Turbo/super = .006" per inch of bore diameter.



    for street, lower hp I would go .005per inch bore, full out race .0055 per bore and what ever you make the top at least the same on the second ring if not .001-.002 bigger, never had any problems that way.
    theirs a saying if you build to tight everybody will know,(BOOM) you build loose your the only one that knows.

    I think i'm going to use .0055 forumla
    3.830 x .0055 = .0021 ring gap 1st and do .0023 for 2nd
    What about the oil catcher rings? .0015? .0019? .0025?
     
  2. TheSilverBuick

    TheSilverBuick In the Middle of No Where

    I always look up the manufacture spec if I can, though they generally all seem to be in the same ball park. Those numbers look like they'd keep you out of trouble.

    Likewise on the second ring being a hair wider.

    I've never gapped the supporting rings of the oil ring, which of course is overlapped.
     
  3. Nothingface5384

    Nothingface5384 Detail To Oil - Car Care

    Yeah I simply didn't know specs for supporting rings
    Imagine there would be a spec sheet in the piston ring box
     
  4. TheSilverBuick

    TheSilverBuick In the Middle of No Where

    No I don't think there is one. they just have like a 1/4" gap (iirc...) as they are not there to push against the cylinder wall they have a fairly irrelevant gap.
     
  5. Alssb

    Alssb Well-Known Member

  6. Nothingface5384

    Nothingface5384 Detail To Oil - Car Care

    yeah i know about them
    I wouldn't want to run a gapless 2nd ring though...sounds like it'd compound the problem of flutter, which is why you're suppose to have a larger gapped 2nd ring versus first
     
  7. 8ad-f85

    8ad-f85 Well-Known Member

    The manufacturer's guidelines are a starting point. If you call them with specifics, they'll suggest something.
    You'll notice those guidelines vary somewhat with piston material.
    If you are running 9000rpm NA, you would want more...Boosted, are you talking about 7 psi or 25? Again, more...
    Bill Trovato says he runs .060" gaps in a Nox Olds with no ill effects.
    That Total seal top rings seems more attractive now, doesn't it?
     

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