Ring gap

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Onder

Onder

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Just eyeballing the internet and saw this comment on a set of rings from 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) show that any gap between .024 to .010 is efficient, and does not show more oil loss than normal gaping at .010 to .014 or does not show any less engine performance, or any extra loss of compression.

I understand that this information might be difficult to accept or understand because the way we have been doing things for the last 80 years but all the rings that are coming out of the USA (Hastings) are using this standard and the gap spec is .020 / JCC and Hepolite are also using this standard

If you are a purest or are racing the bike and want every mechanical advantage possible, we can have custom rings made with a gap of .010 and three piece oil rings, A piston sample is needed for this process.

In most maintenance manuals it says if the gap exceeds .014 then renewal is necessary. This reason is more because if the gap has moved that much you know the knife edge of the rings is worn and or rounded, and at that point there will be so much corrosion from engine gases that the rings need to be renewed.

Comments?
 
I have seen the recommendation before that the top ring should have a bigger gap so gases do move down and get behind the 2nd ring so it beds in quicker. However all the rings having a bigger gap sounds like Wassel speak because they spec'd the wrong gaps and need to sell them. If a bigger gap is good then how do Gapless rings survive.

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I would defy anyone to notice any perceptible or measurable difference between a .020” and a .010” gap!

So my two penneth is it’s really nowt to worry about. But if you are that much of an anally retentive OCD nerd, then use gapless rings and be done with it.

And yes... I’m running gapless rings...
 
Onder said:
In most maintenance manuals it says if the gap exceeds .014 then renewal is necessary.
Click to expand...
If it says that then it's to return the ring gap to standard spec. for maximum service life, I would think but wouldn't say it was absolutely necessary.

For instance, some manuals give a wear limit, a BMW K manual, as an example, ring gap: 0.0079" - 0.0157". Wear limit 0.059".

A Kawasaki factory manual "Piston ring end gap: Top & Second" (converted to inches) 0.008" - 0.014". Service limit 0.028".
 
It’s been known for a long time, by suppliers of rings.

There is practically no such thing as a too-big ring gap.

An enlarged ring gap can be a sign of a worn bore, but a measured and inspected bore is a much more reliable test.
 
kommando said:
I have seen the recommendation before that the top ring should have a bigger gap so gases do move down and get behind the 2nd ring so it beds in quicker. However all the rings having a bigger gap sounds like Wassel speak because they spec'd the wrong gaps and need to sell them. If a bigger gap is good then how do Gapless rings survive.

www.performanceunlimited.co.uk

Home - Performance Unlimited

WELCOME TO PERFORMANCE UNLIMITED Distributors for some of the most respected racing engine component manufacturers PISTONS - BLOCKS - CAMSHAFTS - CONNECTING RODS - CONVERTERS - CYLINDER HEADS - DAMPERS - GASKETS - OIL AND FUEL FILTERS - DRY SUMP SYSTEMS - OIL PANS - ROCKER ARMS Contact us...
www.performanceunlimited.co.uk www.performanceunlimited.co.uk
Click to expand...
I have seen (and I follow) the better recommendation to make the 2nd ring gap 30% bigger than the top ring gap.
 
It relieves pressure between the top and second rings and so allows the top ring to seal better for a greater part of the power stroke.
 
Triton Thrasher said:
It relieves pressure between the top and second rings and so allows the top ring to seal better for a greater part of the power stroke.
Click to expand...

Has anybody actually measured this, or is it someone's mental masturbation?

I suggest your explanation should read "It tends to equalize the pressure between the top and second rings .......(etc).

I am not trying to start an argument, just trying to get an engineering grip on it.

Slick
 
concours said:
This has been discussed.
Ad nauseam.
Click to expand...
This is one subject that has pissed me off in the past. I called hastings about their rings which had a .024" gap for my 260 small block (3.8" bore). They assurred me it was within specs as the industry standard - but it smoked. So I rebuilt it all over again with a tight ring gap - it quit smoking.

Blow by is blow by.

Then I heard about someone going for 0 ring gap on a race Nort when hot and getting more power. I tried it by by using only .008" on my hot race Nort. It ran great.

I also have a problem with the ring flutter because there cannot be more pressure between the rings than there is above the top ring during power stroke - it seems impossible that the top ring could be lifted off the seat if the pressure above it is greater. If more blow by through the 2nd ring is such a good idea then why not make the gap 1/4" wide - or don't even bother installing it.
 
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texasSlick said:
I suggest your explanation should read "It tends to equalize the pressure between the top and second rings .......(etc).
Click to expand...
We want to avoid equalising pressure above and below the top ring.

The pressure that drives the top ring out against the bore is the differential between pressure above the ring and pressure below the ring.

In modern times, these things can be measured- and they have been.
 
Triton Thrasher said:
It’s been known for a long time, by suppliers of rings.

There is practically no such thing as a too-big ring gap.

An enlarged ring gap can be a sign of a worn bore, but a measured and inspected bore is a much more reliable test.
Click to expand...
Rubbish.

A too large ring end gap will result in a marked loss of performance.

End gaps need to be kept right at the lower end on spec for best performance and oil control.
 
Momus said:
Rubbish.

A too large ring end gap will result in a marked loss of performance.

End gaps need to be kept right at the lower end on spec for best performance and oil control.
Click to expand...
Don’t run away with the idea that I’m making this stuff up.
 
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