Piston ring gap size exactness

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Dairymilkbatman
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Piston ring gap size exactness

Post by Dairymilkbatman »

Hi,

I apologize for the noob question, it is a hard question to fully utilize the search engine for.

How exact should ring gap sizing be or to rephrase, am I allowed 0.0005 + / - ?

My .023 feeler gauge fits in the No.1 cylinder ring gap with a little resistance but, upon measuring the No.2 cylinder ring; .023 slips right in with no drag at all and I tried .024 to which I couldn't get it in *pun*. So I guess it's closer to 0.235.

Have I gone too far?
Am I being to fastidious?

Kind regards

.023 is what the piston manufacture recommends for my application.
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Re: Piston ring gap size exactness

Post by mag2555 »

The main thing is that you have enough gap that the ends will not Butt up and break the rings when the motor gets as hot as it will ever possibly get!
That being said even being even .0015" too big is the better way to have be by far!
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Re: Piston ring gap size exactness

Post by blykins »

With precision engine building, we always strive to have everything dead nuts on and put to where we want it to be. However, just like mag says, the jist of it is that you want an adequate gap.

BTW, I'm not condoning just filing the rings willy-nilly without putting effort and precision into it, but if you have one that's a thou or two loose, it's not going to hurt one thing.
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Re: Piston ring gap size exactness

Post by engineguyBill »

mag2555 wrote: Sat Mar 17, 2018 7:13 am The main thing is that you have enough gap that the ends will not Butt up and break the rings when the motor gets as hot as it will ever possibly get!
That being said even being even .0015" too big is the better way to have be by far!
This is correct. The actual dimension of the ring gaps is not important (to an extent), as long as there is plenty of gap so that the rings won't butt together as the engine reaches operating temperature. Remember, the area of the gap measurement is controlled by the piston to cylinder wall clearance. Therefore a variation of a couple of thousandths (wider) will not result in significant leakage here, although the successful high performance engine builder strives to have exact ring gap dimensions when possible . . . . . . . .
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Re: Piston ring gap size exactness

Post by PackardV8 »

Dairymilkbatman wrote: Sat Mar 17, 2018 6:28 amHi, I apologize for the noob question, . . How exact should ring gap sizing be or to rephrase, am I allowed 0.0005 + / - ?
Have I gone too far? Am I being to fastidious? Kind regards.
Yes, that's a bit obsessive, but only if you're charging the customer by the hour to get within .0005" on each of 32 rings.

No, not if you're doing it for your own satisfaction.

Maybe, if splitting half-thous, always aim for the high.
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Re: Piston ring gap size exactness

Post by user-23911 »

You have a nominal measurement with a + and - deviation.
Use 2 feeler gauges, one as minimum size, the other as maximum size.

Use as a go / no go measure.


If you want to be more accurate, make the 2 sizes closer together minimising the +/ - deviation.
Dairymilkbatman wrote: Sat Mar 17, 2018 6:28 am

.023 is what the piston manufacture recommends for my application.
The spec can't be anything other than wrong.
It doesn't give a tolerance.
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Re: Piston ring gap size exactness

Post by k-star »

10 or so years ago I was thrashing on a Friday night to get an engine back to a customer to race on Saturday. The guy helping me missed the top gap by .010, He took it over sized. I had no spares in that size. I had to run it. Told the customer if there was any issues with it I would fix it during one of his off weeks. There was zero difference in that cylinder then any of the other 7. He ran it the entire season, no issues.
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Re: Piston ring gap size exactness

Post by F-BIRD'88 »

If you look at the exposed running ring gap area difference of a ring gap being .010" too big, you can see that in the big scheme of things it is a very small factor.
Always better to be a hair too big than too small "ouch".
If you are making a lot of power per CID then there is more heat load too. so....
if when a ring butts, even for a brief second while running the ring to cylinder seal quality get really torn up quick. This is a much more critical factor (ring to cylinder sealing performance and ring to ring land dynamic sealing performance)
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Re: Piston ring gap size exactness

Post by gmrocket »

Dairymilkbatman wrote: Sat Mar 17, 2018 6:28 am Hi,

I apologize for the noob question, it is a hard question to fully utilize the search engine for.

How exact should ring gap sizing be or to rephrase, am I allowed 0.0005 + / - ?

My .023 feeler gauge fits in the No.1 cylinder ring gap with a little resistance but, upon measuring the No.2 cylinder ring; .023 slips right in with no drag at all and I tried .024 to which I couldn't get it in *pun*. So I guess it's closer to 0.235.

Have I gone too far?
Am I being to fastidious?

Kind regards

.023 is what the piston manufacture recommends for my application.
If you did it again and held the ring in your hand for a bit longer the gap would close up,,I say your good to go.

Your doing a good job...
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Re: Piston ring gap size exactness

Post by swampbuggy »

Good statements F-Bird' 88 IMO, Mark H. :)
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Re: Piston ring gap size exactness

Post by cpmotors »

So, who gaps the rings with a torque plate in place so the bores are the correct circumference, seeing as how your average BBC can distort .0025" on some bores? :D
3.1416 anyone? :)
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Re: Piston ring gap size exactness

Post by Dairymilkbatman »

This is probably the best forum I have stumbled upon, friendly, knowledgeable.

Much appreciated, I can put this together over the weekend rather than waiting for new rings! :D
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Re: Piston ring gap size exactness

Post by user-30257 »

Exactness only matters when you are sneaking up to bring gaps in on rebuilds.

If you are running huge piston to wall clearance then it doesn't matter, you are asking a lotof the rings anyways.
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Re: Piston ring gap size exactness

Post by ProPower engines »

cpmotors wrote: Sat Mar 17, 2018 11:06 pm So, who gaps the rings with a torque plate in place so the bores are the correct circumference, seeing as how your average BBC can distort .0025" on some bores? :D
3.1416 anyone? :)
Any engine that is done with a T/Plate the rings should be check the same way.
I made that mistake once on a BB mopar that was using some KB hypereutectic pistons and after I had to sleeve a hole I check the difference and guess what ](*,) ](*,)
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Re: Piston ring gap size exactness

Post by MadBill »

So how about when checking piston clearances? :-k
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