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piston expander rings question

Discussion in 'The Hokey Ass Message Board' started by atotalnincompoop, Mar 2, 2013.

  1. i am rebuilding a 429 cadillac engine for a friend, the engine was rebuilt a while ago, it quickly began burning oil.

    i took it all apart, the cylinders were glazed, the ring gaps were aligned, its .040 over with replacement pistons.

    i had the block cleaned and deglazed, ordered new bearings, rings and an isky cam for it.
    so today i started to reassemble it, while putting the rings on the pistons, i found that the expander is wider than the one its replacing, it fills that groove so i can't installl the rail rings. i tried the old expander in there and the rails fit. the old expander ring fits in the bore tight.
    which may of caused the engine problem to start with. i think the end gaps on the rail rings is .013, shouldn't the expander be kinda loose in there? or is there an end gap measurement?
    the new expander probably has 1/8" gap.
    im not really sure what is wrong here, the old expander or the new one
    Last edited: Mar 2, 2013
  2. What do you mean "the piston ring gaps were aligned"?????

    I smell your problem and answer in that statement.
  3. n the gaps were aligned on all 8 pistons, this pic is from when i pulled them out...
  4. All gaps should be staggered.
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  5. ya thanks, i know. this is how it came out, we know its wrong:)
  6. It kinda sounds as though the expanders could very well be the wrong ones. Check the end gap on the oil/compression rings and go from there.
  7. the other rings check out fine
  8. My point was that it probably didn't need to be rebuilt, just stagger the rings.

    As far as what you're dealing with now I'd contact the ring manufacturer. Designs constantly change, usually for the better.
  9. looking at the picture of the piston as you pulled it out , it seams to me what you are calling an expander is not's not supporting the rails

    i think the new one is correct. the rails should spiral in on top of those notches
  10. i will contact them on monday.
    the engine needed to be deglazed, indexing the rings wouldn't fix the damage that was done. new rings and new hone, should do it
  11. are you saying that the new rails should sit on the expander with the top of the rail flush with the top of those notches? if that makes any sense how i said it
  12. I've had rings (and other parts) packaged wrong or mis-labled. Contacting the company should straighten things out. The last thing you wanna do is chance it.
  13. im going to go back out to the garage for a second to take a close look:)
  14. Almost always there's a small sheet that comes with rings that will tell you installation procedures. Things like which is the top of a ring and how the oil rings go together is usually on that sheet.
  15. hey, i am an instruction reader, i also ask for directions:D
    in this case the instructions are vague and the picture does not give enough info, i sideways cross section view of the rings sitting on the expander would of been better.
  16. ding ding ding!!!
    you were right! i spiraled them together trying to keep it on the notches instead of falling into the groove, looks like i'm good to go. thanks everyone:)
  17. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 5,034


    Looks to me like the old "expander" is turned 90 degrees, so rather than pushing the oil rails out to contact the cylinder it is just flopping around. No pressure on the oil rails means a lot of oil getting into the combustion chamber. Is there any sign of there having been the little supporting notches on the old expander? The way it was installed they could well be worn off on the side that was contacting the cylinder wall.

    If a novice built the engine and didn't know how to install the 3-piece oil ring, they may well have twisted the expander so that it fit like they thought it should be. Were all 8 installed the same way? They can be re-formed quite easily.
  18. saltflats
    Joined: Aug 14, 2007
    Posts: 10,075

    from Missouri

    Looks like the picture of the oil ring on the piston looks like it was the wrong size oil ring to me.
  19. black 62
    Joined: Jul 12, 2012
    Posts: 1,895

    black 62
    from arkansas

    rings rotate ---so if all the gaps are lined up on one piston that is temporary and will cure it's self---but all eight lined up is a catastrophe---# 17 sounds right to me on the oil ring
  20. R Pope
    Joined: Jan 23, 2006
    Posts: 3,309

    R Pope

    The oil rings you took out are the wrong ones for those pistons. There should be no room for the rings to move up and down in the grooves as there is in the picture.
    The expander you have in the new set is the right one.
  21. Thunderroad312
    Joined: Nov 18, 2012
    Posts: 159


    The expander shown in your photo could not possibly have worked because it was not supporting the scraper rails. That is clearly the problem. Make sure the scraper rails sit on the support notches. You can test their effectiveness by installing just the oil rings without the compression rings and insert the piston upside down in the bore. Holding on to the connecting rod push the piston down in the bore and pull it back. You should feel the drag of the oil rings against the cylinder.

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