Ring end gaps

[Wing It]

Hi everyone.

Building a 440 that is relatively stock. It is .060" over (4.380" bore). Running about 10.3 to 1 compression with forged pistons. My sealed power rings (that are not file fit) have about .028" gap on the top ring and about .026" gap on the second ring. I see the desired spec for a street engine is about .0045" per inch of bore for the top ring which pencils out to .020" gap and .005" gap per inch of bore for the 2nd ring which pencils out to .022" gap. Sealed power installation guidelines found online actually show a little smaller gap for that size bore (.004 top, .0045 2nd, which pencil out to .017" and .020").

The ring gaps now all measure about the same. The piston to cylinder clearance is about .0015".

Why would sealed power sell these rings for this engine with this overbore and make the gap too large?

Looking at these file fit rings as a solution: https://www.summitracing.com/parts/tsr-cr3290-65

Any advice?

 

[GTX JOHN]

You could live with that gap on a street car
No perfect but OK
What worries me is the tight piston to wall clearance
on your forged Pistons = Seems very tight
Are you sure you have 5/64 rings
many aftermarket pistons run 1/16 rings

 

[dvw]

Non file fit are always a touch large. Every .001" in bore increases gap by .00314". Are you certain that the piston to wall is only .0015"? Though that's the recommended min with these pistons it's pretty tight. If the block were machined with a touch more clearance that would explain a larger gap. The ring gap itself is of zero concern. It won't bother a thing. Gap is only to keep the rings from butting when they heat up. That means the gap itself is only maybe .010" when running. Ring seal to the wall and piston groove is way more critical than this small gap. You could run a .040" gap and never notice it.
Doug

 

[Wing It]

Thank you John and Doug!

The box the pistons came in actually lists the minimum piston to bore clearance as .001" The machinist and I both thought that was too tight so we called Sealed Power. An older catalog listed this part number as a requiring minimum clearance of .0015". The Sealed Power Rep stood by the .001" and said that if we went too big we would break pistons. We did end up going to about .002" which seemed to be a happy medium. This could explain a slightly larger end gap.

The Summit listing for the pistons calls for 5/64" compression rings and 3/16" oil rings and that is what I bought. They fit well with the appropriate amount of side clearance.

Here are the Pistons: https://www.summitracing.com/parts/trw-l2355f60

I called a guy who recently built a 528 Hemi for me and he said the same thing you both said about the end gaps being fine.

Thanks for helping out with your advise and such. This forum is fantastic.

Bob