Piston ring end gap

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xring

xring

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The more I read about it, the more confused I get.

On my 4.070 bore small block, using Ross pistons and Sealed Power rings, Ross recommends .004" gap/inch of bore for the top ring, and more for the 2nd ring. Sealed Power recommends .0045"/inch for the top ring, and less for the second ring.

Also I see the resulting 0.018" top ring gap would be considered too tight by some.

I hate to just pick a number I like for ring end gap. Right now I'm sticking with the ring manufacture's suggestions.

Engine specs are 4" stroke, 10.7:1 with ported Eddy heads; Comp XS282S mechanical cam; Holley 870 Street Avenger; Eddy Air Gap RPM. High performance street use.

Thanks.
 
Go with what the manufacturer recommends for the piston and you'll be fine. It's all about how well the piston dissipates heat, how high the top ring land is and how much the piston will expand.
 
ramcharger said:
Go with what the manufacturer recommends for the piston and you'll be fine. It's all about how well the piston dissipates heat, how high the top ring land is and how much the piston will expand.
Click to expand...


There again it is a little confusing; the sheet that came with the pistons says follow the ring manufacturer's suggestions; the Ross sheet that came with the rings (which are in a Total Seal box with a Ross part number sticker) gives the .004"/inch for top ring and (I think) .005"/inch for second ring.

I said Sealed Power before but they are Total Seal rings.

Thanks.
 
I generally go by the piston mfg. cause like Ram said the piston design properties are what mainly determines the gap to run. In your case there's only .002" diff. for either formula you have there so to be safe I'd run it at .018" just so you know it won't butt together.
 
Mine measured out .018"-.021" which was within the piston manufacturers spec for a normally aspirated gas engine. Mine weren't file fit but since they were within spec I put it together; doesn't use oil and no oil blowing out of the breather at full throttle so its all good. The important thing is that the gaps are not too small which will cause rings to butt resulting in catastrophic damage. There are usually different specs depending on how the engine will be run; for example more ring gap for nitrous, turbo, and super charged engines.

The oil rings had real big gaps which I was told was ok.

Your engine combo sounds real good.
 
You really need to compare what the ring manufacturer recommends to what the piston manufacturer recommends, if there is a big difference then call them both and ask them. Piston expansion is the most common way to set the gap but some rings expand more than others and if the gap is too tight, the rings can bind up in the cylinder or piston when it heats up and you can destroy your engine. Also nitrous, turbos and blowers make a difference on what the ring gap is suppose to be set at as does the type of rings you are using.
 
xring said:
The more I read about it, the more confused I get.

On my 4.070 bore small block, using Ross pistons and Sealed Power rings, Ross recommends .004" gap/inch of bore for the top ring, and more for the 2nd ring. Sealed Power recommends .0045"/inch for the top ring, and less for the second ring.

Also I see the resulting 0.018" top ring gap would be considered too tight by some.

I hate to just pick a number I like for ring end gap. Right now I'm sticking with the ring manufacture's suggestions.

Engine specs are 4" stroke, 10.7:1 with ported Eddy heads; Comp XS282S mechanical cam; Holley 870 Street Avenger; Eddy Air Gap RPM. High performance street use.

Thanks.
Click to expand...

Top gap: .020 Second: .026
 
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