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ring gap

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    Senior Member tigertooth's Avatar
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    Default ring gap

    Had a bad leakdown on 2 cylinders. 4-8. Pulled the motor down today and the top and second ring gaps are almost aligned on those two cylinders. Anybody got any ideas on why this happened and what to do to stop it. 509 chevy. Dart block. Je pistons and rings
    Last edited by tigertooth; 03-31-2012 at 06:52 PM.

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    Senior Member ol guy's Avatar
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    What ring gap and how did you stagger on assembly?

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    steelcomp was here
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    Quote Originally Posted by tigertooth View Post
    Had a bad leakdown on 2 cylinders. 4-8. Pulled the motor down today and the top and second ring gaps are almost aligned on those two cylinders. Anybody got any ideas on why this happened and what to do to stop it. 509 chevy. Dart block. Je pistons and rings
    Rings rotate on the piston. Run it some more and they won't be lined up for long. Leak down tests can be really misleading. Were these cyl's down on power or showing bad plug readings or something? What made you leak it down?
    FWIW...gaps being in line shouldn't really effect the leak down much. You might look for something else.
    Last edited by scott foxwell; 03-31-2012 at 07:49 PM.
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    Senior Member tigertooth's Avatar
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    Quote Originally Posted by steelcomp View Post
    Rings rotate on the piston. Run it some more and they won't be lined up for long. Leak down tests can be really misleading. Were these cyl's down on power or showing bad plug readings or something? What made you leak it down?
    FWIW...gaps being in line shouldn't really effect the leak down much. You might look for something else.
    Just doing normal maintenance on a drag race motor with about 150a passes on it. How would I be able to tell if a cylinder was down on power other than a leak down test

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    Senior Member tigertooth's Avatar
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    Quote Originally Posted by ol guy View Post
    What ring gap and how did you stagger on assembly?
    I would have to get back to you about the exact gap as my data is 17the miles away from me right now. They were gapped to Je specs for a nitrous motor with a 4.5 bore and installed 180 degrees apart with the oil ring 270 apart under that with the expander in line with the gap in the second ring.
    Last edited by tigertooth; 03-31-2012 at 08:40 PM.

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    gn7
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    Quote Originally Posted by steelcomp View Post
    Rings rotate on the piston. Run it some more and they won't be lined up for long. Leak down tests can be really misleading. Were these cyl's down on power or showing bad plug readings or something? What made you leak it down?
    FWIW...gaps being in line shouldn't really effect the leak down much. You might look for something else.
    Rings spin like tops. Possibly worse in a BBC than any other engine. Not really sure why its worse, possibly the piss poor rod ratio. They will spin bad enough to micro weld in the ring lands on long hi RPM situations or even short extreme RPM conditions.
    There isn't much you can do to stop it. But like Steel said, it alignment won't last long. Its one of the reasons I kind of chuckle at the idea of the "exact" gap alignment when assembling an engine. You mind as well jack up you car and align all the tire valves, they will probably stay align about as long.

    Like Steel said, leak downs can be very misleading. All data of any kind can be misleading. I use a leakdown to tell me if the exhaust, or intake is leaking, or if the majority is thru the rings. If its past the rings, it has to be pretty bad and show some significant signs of blowby for me to be that concerned. Running cylinder temp is a huge deal and almost impossible to duplicate.
    If there is no signs of oil on the plug, or bad blowby, I can't get to excited about a couple % on a leak down.



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  9. #7
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    Quote Originally Posted by tigertooth View Post
    Just doing normal maintenance on a drag race motor with about 150a passes on it. How would I be able to tell if a cylinder was down on power other than a leak down test
    Performance, maybe? A leak down is a static test and really doesn't tell you anything about a running engine. It might help tell you something about a poorly running engine or an engine with an obvious problem, but I wouldn't bother leaking down a perfectly good running engine. It'll drive you crazy.
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    Quote Originally Posted by gn7 View Post
    Rings spin like tops. Possibly worse in a BBC than any other engine. Not really sure why its worse, possibly the piss poor rod ratio. They will spin bad enough to micro weld in the ring lands on long hi RPM situations or even short extreme RPM conditions.
    There isn't much you can do to stop it. But like Steel said, it alignment won't last long. Its one of the reasons I kind of chuckle at the idea of the "exact" gap alignment when assembling an engine. You mind as well jack up you car and align all the tire valves, they will probably stay align about as long.

    Like Steel said, leak downs can be very misleading. All data of any kind can be misleading. I use a leakdown to tell me if the exhaust, or intake is leaking, or if the majority is thru the rings. If its past the rings, it has to be pretty bad and show some significant signs of blowby for me to be that concerned. Running cylinder temp is a huge deal and almost impossible to duplicate.
    If there is no signs of oil on the plug, or bad blowby, I can't get to excited about a couple % on a leak down.
    Cylinder finish (specifically cross hatch angle) has a lot to do with how badly rings spin.
    Running cyl temp, yes, but more than that, running cyl pressure is absent wen doing static testing. Load that cyl. with 1200psi and see what happens.
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    Senior Member tigertooth's Avatar
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    Thanks for the input guys. I had no idea the rings would spin but can see how crosshatch angle would effect it. Engine was down in power to the tune of about. 015 in the quarter mile. Doesn't seem like much but it will cost you the race if the boat is tuned for a perfect et and it slows down that much. Engine was also puffing a little smoke out if that side when we warmed it up. What do you guys think if total seal rings.

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    Distinguished Member David 519's Avatar
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    Quote Originally Posted by gn7 View Post
    ...... All data of any kind can be misleading......
    Man, there's a quote to live by.... and it might become a siggy!! I do engineering testing for a living, have for almost 30 years and recently been asked to help work with a few new(er) engineers. I tell them time and again, in order for data to be meaningful, you have to completely understand both the testing process, AND the science behind what you're looking at.
    Bottom line is, whether you're flowing a set of heads or evaluating the structural response of a large vertical pump, if you don't uderstand the measurment process (to qualify the data) and why the system behaves as it does, you're probably pissing in the wind. Moreover, if you're following a procedure someone else developed with litle understanding of why it works, you WILL screw something up and won't have a clue why..... You wanna become a guru like GN, get a handle on math/physics and maybe a bit of thermo and some dynamics. Learn to look at everything critically and if you don't understand something, learn it. Lastly, develop a list of trusted group mentors/peers to work with and bounch ideas off.

    Quote Originally Posted by tigertooth View Post
    Thanks for the input guys. I had no idea the rings would spin but can see how crosshatch angle would effect it. Engine was down in power to the tune of about. 015 in the quarter mile. Doesn't seem like much but it will cost you the race if the boat is tuned for a perfect et and it slows down that much. Engine was also puffing a little smoke out if that side when we warmed it up. What do you guys think if total seal rings.
    To little data for me to go off of, but how closely do you watch you're valve spring pressures? In our asphalt car, we would notice the MPH drop a couple if we weren't checking them enough. If we ignored it a bit longer, ET would start falling off. That's when we started checking seat pressures every couple races instead of a couple times a season.
    Quote Originally Posted by gn7 View Post
    ....... David 519 is 100% correct........

    Quote Originally Posted by fuelinmyveins82 View Post
    .....I think people forget that racing is supposed to fun. Losing shouldn't be discouraging it should motivate you work on your pile to make it faster.....

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    gn7
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    Quote Originally Posted by David 519 View Post
    Man, there's a quote to live by.... and it might become a siggy!! I do engineering testing for a living, have for almost 30 years and recently been asked to help work with a few new(er) engineers. I tell them time and again, in order for data to be meaningful, you have to completely understand both the testing process, AND the science behind what you're looking at.
    When we first used our data recorder I remember looking at the read out and thinking, WOW, this is great!!! Now what the hell do I do with all this info.
    Very first thing I learned was, with the exception of oil temp and pressure, not much was of any use on the first run, or the 2nd, or the 3rd, or.......
    You really can't learn much from a small sampling of data. Until you have a small mountain of info under varying setups and conditions, its almost impossible to make an educated decision based on the info. All "experience" is is the knowledge gained thru the years of what does what and what combos worked and want didn't. Some from memory, some from written down. Now, alot from recorders. But with out a LOT of info to compare it to, its basically useless.
    Doing a leak down without many previous leak downs under near identicle conditions, compared to actual performance runs and times is of little to no use.

    Quote Originally Posted by steelcomp View Post
    Cylinder finish (specifically cross hatch angle) has a lot to do with how badly rings spin.
    Running cyl temp, yes, but more than that, running cyl pressure is absent wen doing static testing. Load that cyl. with 1200psi and see what happens.
    Ring rotation is almost entire due to cylinder finish. Cross hatch angle, finish, straightness, and roundness. Wouldn't doubt if the thickness of the cylinder walls, ring thinkness, ring tension and cross section, bore diameter, and stroke/piston speed all play some roll.
    I know I never experienced the ring rotation in a small block with a 4.00 bore and 3-3.25 stroke That I see in a BBC.

    The dynamics of a running engine can never be duplicated in a shop with a static engine, even heated. There is virtually no way to know how well a ring is sealing on the trailer. I guess thats why more and more dyno rooms are equiped with AVI blowby meters.

    I have had an air hose hooked to a cylinder more than a time or two in the past couple years, but I am not really sure where my leak down meter is even at! All I am really interested in is a BAD leak, and from where. Don't need the meter for that



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    Senior Member tigertooth's Avatar
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    Quote Originally Posted by gn7 View Post
    When we first used our data recorder I remember looking at the read out and thinking, WOW, this is great!!! Now what the hell do I do with all this info.
    Very first thing I learned was, with the exception of oil temp and pressure, not much was of any use on the first run, or the 2nd, or the 3rd, or.......
    You really can't learn much from a small sampling of data. Until you have a small mountain of info under varying setups and conditions, its almost impossible to make an educated decision based on the info. All "experience" is is the knowledge gained thru the years of what does what and what combos worked and want didn't. Some from memory, some from written down. Now, alot from recorders. But with out a LOT of info to compare it to, its basically useless.
    Doing a leak down without many previous leak downs under near identicle conditions, compared to actual performance runs and times is of little to no use.


    Ring rotation is almost entire due to cylinder finish. Cross hatch angle, finish, straightness, and roundness. Wouldn't doubt if the thickness of the cylinder walls, ring thinkness, ring tension and cross section, bore diameter, and stroke/piston speed all play some roll.
    I know I never experienced the ring rotation in a small block with a 4.00 bore and 3-3.25 stroke That I see in a BBC.

    The dynamics of a running engine can never be duplicated in a shop with a static engine, even heated. There is virtually no way to know how well a ring is sealing on the trailer. I guess thats why more and more dyno rooms are equiped with AVI blowby meters.

    I have had an air hose hooked to a cylinder more than a time or two in the past couple years, but I am not really sure where my leak down meter is even at! All I am really interested in is a BAD leak, and from where. Don't need the meter for that
    Now that I know that I need to throw my leakdown tester away what do you gurus of engineering marvel think of total seal rings

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    Senior Member EVILFORCE's Avatar
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    Anyone ever run a pinned ring?
    No Fool Like A Old Fool is there?

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    gn7
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    Quote Originally Posted by EVILFORCE View Post
    Anyone ever run a pinned ring?
    In every 2 stroke I ever owned

    for Gapless 2nd , May be some benefit to them in a alky deal, and some claim there is a benefit in Alum blocks. Personally I won;t let them near my engine. AGAIN its one of those DYNAMIC things. May seal great in a static engine on the trailer, but not all that in a running engine.

    Gapless top rings. May very well be some thing there. I haven't tried them yet, but they are on the "consider trying" list. Expensive, and not sure if they are worth it. Not much gets past that tiny ass little gap when the engine is warm, the gap is tightened, and the piston is moving 6000 ft per minute with 1200 psi loading the ring against the wall and the bottom of the ring land.
    Cylinder finish and straightness play a much much bigger role in power than the gap in the ring.
    I rather have a used plasma moly gap type ring on a GREAT cylinder than a new gapless ring in a so so cylinder



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    Last edited by gn7; 04-01-2012 at 05:59 PM.

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