Gapless rings??

[Todd Baumann]

Hey guys,
Was wondering if anyone had any experiences with gapless rings and what are the pros and cons of using them are.
Thanks for the input,
Todd

[niles]

You cant do that; the reason for the gap is that has the ring heats up and expands and the gap goes close to zero. If it goes to zero the ring seizes in the bore ripping the top of the piston off.
gn

[Satanpez]

If that was true, Gapless rings wouldn't exist.

-steve in nj-

[Cobranut]

Niles,

Funny, My motor has gapless rings from Total Seal and it hasen't siezed yet.

Actually, they are really a multi-piece second ring, which has the gap bridged, creating a better seal.
The top ring is conventional.

They're worth just a few horsepower when new, but they probably hold the seal better as the miles add up.

Later,

[ERA535]

Gapless rings are actually two rings in one groove that overlap so that there is no gap.

I used to use them in Formula Vee and Formula Ford engines where every last horsepower was precious.

I must say that I could not tell the difference between them and a good iron ring which would "break in" quickly. (something you want in a race engine)

Leak down difference on a broken in engine between gapless and non gapless was in the order of 2%.

Bottom line - in a high horsepower street car you will not be able to tell the difference.

My opinions obviously!

[Jeff Frigo]

Here you go:


Total Seal Gapless Rings

[Turk]

Everybody is right.
They are gapless!
They also have a gap.

I am using them as well.

TURK

[Mr.Fixit]

They are prone to "fluttering" if used without a vacuum pump to draw on the crankcase, or so I have been told.

[ERA535]

Exactly right!!

In fact when standing next to the dyno in Ohio I noticed, on each run, evidence of ring flutter on Turks car....I made that comment to someone standing next to me...was it you Steve R?

We used to run a crankcase vent line to the exhaust for this as well....

The memory is a terrible thing to .....oh well, I can't remember the saying.

[Turk]

First a Heart Murmur....
Now I have Ring Flutter!!!

What is next?
Valve Lash?

TURK
Let's hope someone doesn't tell me I am Ugly too.

[SFfiredog]

Gapless rings are another hotly debated issue in the engine building community. Some swear by them, others swear at them.
The theory of gapless rings is understandable, no gap, no compression loss by the rings. according to some, it is not that simple. The top ring on a gasoiline engine should be doing the combustion gas retention the second ring is more of an oil control ring to wipe the cylinders clean. The oil ring is designed to distribute the oil to the cylinder wall. Most gapless rings are installed in the second ring land. Some say that the gapless second ring creates a low pressure area ( no Turk, not that kind of low pressure area, it won't rain inside your cylinders ) which causes the ring to "flutter" in the ring land which will eventually wear the ring land and cause poor ring seal. Some piston manufacturers cut a groove between the 1st and 2nd rings in an attempt to equalize the pressure between the rings. The contention is that when the engine is static and a leak-down test is done the leakage numbers are very low, from 0 to 3 percent. But, when the engine is running, the rings "move around", causing poor cylinder sealing. There are new design gapless rings coming that are suppose to address this issue. Ring sealing is a constantly evolving science and new ideas and theories a coming all the time.
HTH,
Mike

[niles]

Gap no gap; gees it makes my head hurt. Reminds me of last yrs " what'a the definition of sex". Rings must have "clearance" because they expand at .00000065 in/in/deg = about .008 inch for a 4 in piston. ERA535 is right on; the leak down is hardly measurable; it's even less that that; why, where does the 2% leakdown go? to the second ring. Now you have .02x.02 for a whole ..0004 or .04% leakdown. Now where does that go? to the oil ring which is designed to have an oil sealing feature and is very effective at stopping any leakage that gets that far.

However; the the most important factor is: the bridge has 2 90 deg edges per ring side, these are "stress risers" that are cyclic fatique failure sites. Now you have 4 per ring, one bridge piece, x2 ringsx8 cylinders; you have just increased the odds of a material failure by 80 times. Granted the probablity of a ring failure is low; but why increase any odds 80X. In dirt farmer language, the odds of getting hit by lighting is very small, but you don't walk around a golf course swing a club in a lighting storm.

No production engine used these kind of rings because they are not as reliable. Stick with a properly end gapped std ring. They have stood the test of fire and time for good reasons.

gn

[TAB]

Thanks for the replies guys,
My mechanic thinks they will help my problem of having the rings unseat themselves, I personally don't know and am not sure if that really would eliminate what happened the first time or not. The only ones that I have been able to find were the ones that Jeff had identified. Total seal. Sounds like it couldn't hurt to try them either way.
Todd

[Mr.Fixit]

What do you mean :

"help my problem of having the rings unseat themselves"

[Jeff Frigo]

Total Seal is in the process of coming out with a gapless ring that goes in the top ring grove. You might want to call them.

[Jack21]

Ditto the above about Total Seal bringing out a gapless ring that goes in the top ring grove. They might even have a web site.

The other manufacturer of gapless rings that I'm aware of is Childs & Albert. Might look them up also.

Almost sprung for a set in my own engine. They are supposed to increase engine vacuum to the extent that some folks install restrictor orifices in their PCV line.

The major advantage, as I understand it, is that as the rings wear with mileage, the gapless feature maintains the ring seal, whereas a conventional 1 piece ring gap opens up allowing blowby.

Might be a good question to ask, "Howcome the automakers don't use them?" The automakers don't use roller rocker arms either.

[Cobranut]

The reason the OEM's don't use them is cost. Every dollar they put into the car is a lost dollar of profit. Ditto on the rockers.

[Jack21]

Agreed. If you're going to be re-ringing your engine every 30k - 50k miles, it's a waste of money.

That being said, some of the newer HP pistons available from Probe, TFS, and others are using 1/16" rings. Good for racing, but not so good for mileage. If I didn't want to be replacing rings every 30k - 50k miles, the gapless rings from either Total Seal, or Childs & Albert might be just the ticket for extended mileage with a performance piston.

So, the question is, those of you using gapless rings presently, any problems or complaints?

[Anthony]

Very debatable.

I was talking with a guy who vintage races his CSX3000 cobra, and builds engines, and he said that with the gapless ring in the second position, it doesn't let the high pressure gas to escape from between the 1st and 2nd rings just after the compression stroke, and doesn't allow the rings to "settle" and seal effectively. He doesn't use them. I then emailed this to total seal, about 4 months ago, and the tech emailed me back that it was a complex answer, and to call him for the explanation, which I never did.

Another guy, a highly recommended engine builder told me that they do have lower leak down rates, but that doesn't mean a loss of horsepower. With the engine running, at high rpm's, even with a higher leakdown rate, standard gap rings seal effectively, and he doesn't think it would make a significant difference in horsepower. He thinks the gapless really don't make a difference, and thinks they are a waste of money. Interesting though, he said that he bored out a 427 so, and the next day checked it with a bore gauge and it was .003" out of round. He torked the deck plate back on, and the cylinder went back into correct shape. Point is, I think it's critical to at least hone the block, and preferably bore the engine with a deck plate on to ensure a concentric bore, especially on a thin walled engine block. I think that a concentric bore is more critical for effective ring sealing than whethere or not you're using gap or gapless rings.

[Anthony]

Well, I gave total seal a call, and spoke with one of their techs, and he said there can be a problem with ring flutter (when excessive gas pressure builds up between the rings and prevents effective ring sealing) when using their gapless 2nd rings with 13 - 14:1 compression engines, running with highly efficient exhaust gas headers at high rpm's, greater than 7500 rpm's, i.e. winston cup engines.

He said there shouldn't be any problems with any street or moderate performance engines.