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Hot Rods Piston Ring Qustion

Discussion in 'The Hokey Ass Message Board' started by johnod, Mar 20, 2019.

  1. johnod
    Joined: Aug 18, 2009
    Posts: 780


    I'm putting together a OT engine, but the question remains the same .

    Why do they tell you to position the ring gaps at certain point?
    Once the engine starts the rings will rotate.
    I'm sure they don't all rotate in sync , so what's the point ?

    Been wondering about this.

  2. dana barlow
    Joined: May 30, 2006
    Posts: 3,966

    dana barlow
    from Miami Fla.
    1. Y-blocks

    So you don't start out with bad all lined up gaps. Yes they run n rotate,but how much depens on hone job,that no ring designer can know,so best guess is start as sheet said.
    blowby and loudbang like this.
  3. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,255

    Rusty O'Toole

    If the rings all line up you will get blowby. Best to start them out staggered evenly around the piston, give your engine a chance.
    alanp561, Frankie47 and loudbang like this.
  4. In theory with a good hone job, they will all probably rotate about the same. If one rests over the piston pin, it probably won't be there for long.
    loudbang likes this.
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  5. Mike VV
    Joined: Sep 28, 2010
    Posts: 1,985

    Mike VV
    from SoCal

    The rings don't move as much as you might think, especially in a lower rpm engine. I've taken 7500rpm race engines apart after a season, the rings were VERY close to where they were when I put it together..! And that small distance...I could have moved them with the ring compressor during installation, or moved them taking the pistons out.

  6. buffaloracer
    Joined: Aug 22, 2004
    Posts: 799

    from kansas

    On my drag race engines I don't see all that much rotation. Granted they don't go many miles between teardowns. Leakage is loss of HP.
    dana barlow and egads like this.
  7. johnod
    Joined: Aug 18, 2009
    Posts: 780


  8. greg32
    Joined: Jun 21, 2007
    Posts: 2,043

    from lemont,IL

  9. sliceddeuce
    Joined: Aug 15, 2017
    Posts: 2,982


    So......Explain the tabs on Hudson rings that held the gaps aligned vertically.
  10. jaw22w
    Joined: Mar 2, 2013
    Posts: 1,038

    from Indiana

    I know that 2 stroke engines have a pin in the ring groove to locate the ring gap to keep the ring end from catching in the ports. Makes me wonder about the need or desirability for the rings to be rotating anyway.
    Joined: Jun 3, 2005
    Posts: 8,049


    I was inside my old racer after 400+ rounds of competition. The rings were where I left them. I ran the Total Seals also, only 2% leak on 2 out of 8 cylinders, the rest were between 1 and 2%. The worst of the 8 had a crack in the #6 cylinder wall which was a common problem with those blocks on anything over over .060.
  12. Dwardo
    Joined: Aug 1, 2017
    Posts: 71


    Stock Hudson pistons have a pin in them that fits the notch in the rings to keep them from rotating. I think Rolls Royce did that too. I doubt there was any advantage to it but it was one of many "fine Hudson features" that made them rather expensive cars.
  13. if the ring rotate, how do they get stuck in the piston when I tear it down to rebuild it?
    BJR likes this.
  14. BJR
    Joined: Mar 11, 2005
    Posts: 6,398


    Lots of carbon.:)

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