Ring gap

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Steadfast Cycle:

The new industry standard for British motorcycles is to gap the rings at .020 / New independent lab tests and studies (in the USA and England)"

Deadlast Cycle fails to substantiate the claim with such "lab tests"
Furthermore, the laws of physics didn't change overnight.
And, internal combustion performance & longevity has been tested/refined to hell & back.
"Doctor" Warren Johnson comes to mind as just one example. Smokey Yunick....
Wide gaps are baad, m'kay

Triton Thrasher said:

"Nobody has to worry about it, but improving compression, performance and oil consumption is not “excessive” on any engine."

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Well, maybe my choice of words - "worrying" was a poor one. I totally agree that finding the optimum setup for every individual engine is a good thing to do and 'identical' original factory engines will require slightly different setups to achieve that. Heck, I've seen static timing for optimum performance on two identical stock engines to be 6 BTDC on one an 14 BTDC on another!

But my point is that changing the ring gap within the range specified by the manufacturer is not going to produce any magic HP. In engine building, the "standard" for ring gap for many years has been .004" per inch of bore. If you set up a normally aspirated engine using that 'formula' there will be no issues at all with oil burning or power assuming the bores are properly prepared.

Sure, on a very highly tuned competition engine, adjusting the ring gap to something different may yield a measurable performance gain or better reliability at max power for a race. But on street driven, high performance motors we did lots of dyno testing and never found that changes in ring gap between the max and min manufacturers specs made a consistent difference in power. For that matter, gapless rings didn't consistently show any difference to regular rings gapped at the .004"inch of bore.

We may be at cross purposes. I’m not advocating that a top ring gap larger than standard gives any advantage.

If anyone wants the report on large gaps feel free to email me for a copy.
The report was produced in the US by a ring maker, not sure what one though.

Madnorton said:

If anyone wants the report on large gaps feel free to email me for a copy.
The report was produced in the US by a ring maker, not sure what one though.

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I think Hepolite researched it quite a long time ago, when they were manufacturing in the U.K.

I use total seal 2nd rings with no gap. I don't have any blow by. The bike runs great and the oil stays cleaner with the total seal rings - and this is with over 50,000 miles - still no smoking and oil consumption is low. This is with modern pistons. My previous Hepolite pistons with regular rings were smoking by 50,000 miles.

I think the ring flutter problem has been solved with modern high tension thin rings. I'm not seeing any evidence of ring flutter and I have revved my 750 over 8000 RPM.

The problems I have had (other than worn out bores) is from the ring lands getting loose from the vertical pounding of the rings and so far this has only happened with cast Hepolite pistons. I haven't seen it with the modern pistons yet. Once you get to .006" ring land clearance the Hepolite pistons have blow by and smoking. Modern pistons come new with only about .0015" ring land clearance.

Interesting?

jseng1 said:

The problems I have had (other than worn out bores) is from the ring lands getting loose from the vertical pounding of the rings

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I would be more inclined to believe it was caused by ring flutter

bill said:

I would be more inclined to believe it was caused by ring flutter

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Not a chance.

That was on a street bike with Hepolite pistons that never saw enough revs to experience ring flutter. Loose pounded out ring lands are a common problem with worn out Hepolites. Once you can fit a .006" feeler gauge under your ring - your pistons are junk and smoking.

I had the same problem with my small block Ford. The ring lands pounded out so bad and got so loose that one of the rings broke and took out part of the piston. This was a low RPM truck motor than never revved to ring flutter range.

Ring flutter is purported to be a high RPM problem - usually extreme RPM and I think it gets more talk and hype than it deserves. Most of what you hear about ring flutter and wide gaps on the 2nd ring is BS. Total seal gapless rings are very successful. The people at Total seal are arrogant and flying high and their competition hates them for it. But the fact is that in almost all cases - a gapless 2nd ring gives you a tighter, cleaner and better running motor. The way to prove it to yourself it to try it.

see this video at around 5 minutes:

Some might know more than the manufacturer CP Carillo, but I sure don't. They are the top piston/ ring/ rod manufacturer, most would agree. Incredibly high quality stuff, but a bit pricey, naturally.
I followed their instructions on the 1360 as it has CP Carillo forged pistons and chrome rings.
No blowby issue there.

More recently it was time to set the gaps on the 920 pistons and I used their numbers again on the RGM piston rings, adjusted for 81 mm bore. 14 thou top, 20 thou second 15 thou oil is what it is at.
Will see how that works.
If old style smaller , even gaps worked better, wouldn't CP Carillo instruct to do that?
If gapless gave more power or longevity, wouldn't they know about it and go that route?

Setting the rings this way is not really fussing as it's easy peasy to file a few thou extra off the rings at install.
Obviously one shouldn't pull working motor apart to do this, but for a new installation, why not?

Glen

We always custom-set the ring end gap, filing the rings to produce the appropriate gap for .004" per inch of bore. That always produced easily measured HP/torque gains over installing a set of pre-gapped rings, like those you would receive if you order a set of rings for X engine.

Gapless rings consistently provided a bit more power than custom-filed rings on the dyno. That being said, when we used them, it was on certain types of competition-only engines, not on street-driven engines. That was as of 10 years ago or so, when I quit doing any of that work professionally so the design/materials of the rings may have changed but I do know there are still engine builders who do not use or recommend them for street engines due to long-term oil control issues and reduced longevity/increased wear.

I suggest folks interested in using them do some research on impartial sites to see what the current view is toward gapless rings. It is my understanding that no manufacturers use them but again, that may be based on 10-year old info that is not current.

worntorn and mexico mike

As I mentioned in an earlier post - I gapped my racing 750 73mm rings all the way down to .008" .008 to .0010") because I met someone else at the track who recommended tighter gaps.

The result was less blow by and more power. Larger gaps bring the opposite. .004" gap per inch is more than necessary and manufactures recommend wider gaps because they are afraid of liablilty. But for anything without nitrous or turbo - .003" or .0035" per inch is fine and gives better results.

There is no downside (other than the extra expense) to the gapless ring in my experience after using them for 10 years on the street now. Only positives . I push closer to the limits and go for .003" to .0035" per inch on the top ring and a gapless total seal 2nd. Or you can use a gapless top but then you need teflon guide seals to prevent sucking oil because of increased vacuum.

You will never see one piston or ring manufacturer praise the superior qualities of another manufacturer.

Here's an interesting discussion on gapless and also an accidental " out of spec" race engine that kept winning. On teardown it was found to have wider than normal spec ring gaps.
The other interesting observations came from the Dyno operator.
The commenters appear to be unbiased, that is not selling a product.

and I will still stand by what I stated if you run a gapless second ring or a tighter second ring gap you can have ring flutter. it does not matter if it is a high RPM race motor or a water pump motor the lower speed motor just takes longer to beat out the ring groove. also the only POUNDING a ring might see is from detonation.

These guys actually built engines with different ring gaps, then measured the results: http://diagnosticengineers.org/journal_ articles/Ring Gaps vs Knowledge Gaps.php
A little reading on ring grooves: http://blog.wiseco.com/ring-grooves

Bill -how do you verify actual evidence of ring flutter in a Norton? Where is the proof that pressure builds up higher between the rings than above the top ring on the power stroke? It seems like this could only happen on the exhaust stroke (if there was leftover pressure between the rings). The "pounding" I'm talking about is reversion, inertia and friction that causes ring lands to loosen on all pistons over time.

Worntorn - yes I read that article. The opening discussion is negative but ends with "I think they are a very good ring setup for methanol dirt track engines , but not drag racing so far from what i've seen". - No reason is given why they work "very good" for one type of racing but not another.

Gapless top rings are also available and there are lots of claims that they make more power than using conventional rings. The gapless top ring would seem to do away with the trapped gasses ring flutter argument. But then you have to use better guide seals because of increased vacuum and most Nortons have weak guide seals.

Mikeinidaho - That article says that there is no point in staggering ring gaps. My personal experience is that I rebuilt a VW for a friend and it ran great for years. Then all of a sudden it started smoking on one cylinder (it would smoke, then stop smoking, then smoke again). We tore it down and found that the ring gaps had rotated and lined up on the smoking cylinder - we tore it down for nothing - we could have just waited for the ring gaps to rotate and be staggered again.

Does anyone really believe that wider ring gaps are better? Can they prove that by making the gaps wider and wider? Anyone ready to try 1/16" or wider ring gaps and show us the results? I can see an advantage of eliminating the 2nd ring once you get a perfectly sealing top ring with no blow by - but wider gaps than necessary on the top ring can't be right.

There are plenty of mentions of ring flutter on the net - and then there is this:
"you will always have more pressure above the top ring than below it during combustion because the void below the top ring only sees leakage through the end gap. It has to be less than whats above it. Ring flutter is a catch all that gets used when someone doesn't know why their engine doesn't seal as it should."

jseng1 said:

Does anyone really believe that wider ring gaps are better?

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Has anybody said that?

It’s being suggested that 2nd ring should be bigger than top ring gap. I can’t see where anyone is just saying “Ring gaps should be bigger.”

jseng1 said:

you will always have more pressure above the top ring than below it during combustion

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Yes, but will you always have sufficient pressure difference?

This is why ring flutter is no longer a problem with modern Norton pistons using thinner rings:

"The level of piston acceleration at which ring flutter begins can be raised by decreasing the mass of the ring. . . we can take it out of the engine running range."

Modern Norton pistons now use .040" thick top rings instead of the old .062" (.062" is still used by Hepolite and JCC). The thinner rings have less friction and that means more power. The thinner lighter rings do not have as much inertia and do not loosen up the ring lands as bad as the thick Hepolite rings - you get a longer lasting piston and less blow by with thinner rings.

See the whole article at:

Modern Norton piston with .040" top ring

kommando said:

........ If a bigger gap is good then how do Gapless rings survive.

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To answer that question you need to look at how gapless rings work! For a start they aren't actually gapless!

They are a two piece ring, each part does have a gap, and you fit them so that the gaps don't overlap, to create a gapless effect!