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Thread: Ring Wear Question

  1. #1
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    Default Ring Wear Question

    Several times now I put new rings in this troublesome motor I've been messing with, and each time after I pull her down again the rings have about an 1/8 inch gap. They went in there with about .012 inch gap, yet...

    Is this normal after rings break in? The compression readings are holding at a reasonable level (and even increased a bit with running). In every case, the motor had less than a few hours running, and not at WOT for more than a few seconds at a time. Oil level mixture 30:1 initially down to 45:1 after break in.

    Jeff
    "We live at the bottom of an ocean of air." - General Marvage Slatington

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    Were they oversize rings filed to fit standard bore?

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    Team Member zul8tr's Avatar
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    Jeff

    What difference in bore diameter are you measuring. To go from a gap of 0.012" to 0.125 is an increase of 0.113" in ring circumference. That would mean an increase in bore diameter of about 0.113/Pi = 0.036", way huge? Are you getting that same increased ring gap in all the locations in the cylinder you measure?

    Strange that so much wear occurred with that oil mix?

    What kind of rings are you using, OEM NOS, or--?
    Maybe they are made in China?
    " Three may keep a secret if two of them are dead" Ben Franklin
    " ------- well Doctor what have we got a Republic or Monarchy? A Republic he replies if you can keep it"
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    They are .015 oversize cut to fit a standard bore. Genuine Merc rings. All 6 rings wore the same (actually 5--one of them broke on me). I assume the rings wore, not the bore, but I'll re-measure.

    So, this is NOT normal after such minor running? It happened twice with the engine (early Merc triple).

    Jeff

    PS: Thanks for the inputs.
    "We live at the bottom of an ocean of air." - General Marvage Slatington

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    Team Member zul8tr's Avatar
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    If just the rings wore and bore in spec that would mean to me soft metal rings. Other than that it is strange. Post over at JOMS maybe some there have had this, I certainly haven't.

    These are 3 ring deflector pistons in that triple for an early Merc.

    What wear marks are on the sides of the pistons and the bore? Pics.

    Any burrs on the ports and rings are well locked with the pins?
    " Three may keep a secret if two of them are dead" Ben Franklin
    " ------- well Doctor what have we got a Republic or Monarchy? A Republic he replies if you can keep it"
    Benjamin Franklin, 1787 Constitutional Convention, as recorded by signer James McHenry's in his diary at the Library of Congress

    Location: SW Orlando, Fl

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    I had 2 ring slugs in there, and they looked excellent (as did the bores). It appears only the rings are wearing, not the bores. (They are genuine Merc rings, by the way.)

    I'm baffled as well. Found a 3 ring piston that I'm going to use in the top cylinder (where the ring broke). The old piston had a bad spot leading to the second ring at the anti-rotation pin (that was not there before I'm fairly sure of). Perhaps that's why the ring broke? Anyways, the compression in the other two holes was good: 140 to 150 regardless of the wide ring gap--so I'm gonna try again.

    Thanks for you inputs.

    Jeff
    "We live at the bottom of an ocean of air." - General Marvage Slatington

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    Team Member zul8tr's Avatar
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    Persistence required here
    " Three may keep a secret if two of them are dead" Ben Franklin
    " ------- well Doctor what have we got a Republic or Monarchy? A Republic he replies if you can keep it"
    Benjamin Franklin, 1787 Constitutional Convention, as recorded by signer James McHenry's in his diary at the Library of Congress

    Location: SW Orlando, Fl

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    Jerry Wienandt
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    Fastjeff57, please drop me a note to tridentracing@new.rr.com

    I have some experience with Merc triples and Merc rings.

    I have a short document I'd like to send you...

    Jerry

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    Team Member zul8tr's Avatar
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    Jerry

    Please post your info here as well so we can all benefit from your expertise. Sure would like to know what strangeness is going on with these rings.
    " Three may keep a secret if two of them are dead" Ben Franklin
    " ------- well Doctor what have we got a Republic or Monarchy? A Republic he replies if you can keep it"
    Benjamin Franklin, 1787 Constitutional Convention, as recorded by signer James McHenry's in his diary at the Library of Congress

    Location: SW Orlando, Fl

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    Me too!

    Thanks, Jerry.

    Jeff
    "We live at the bottom of an ocean of air." - General Marvage Slatington

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