Piston Ring End Gap

[Crew Chief]

This might draw a lot of different suggestions, however here it goes.

What would a recommended piston ring end gap be for a circle track 358 cu. in. engine on racing gasoline and on asphalt.
The engine is a full roller set up with brodix flowed aluminum heads, 13.5:1 Diamond pistons and a 4.060 bore.
Top ring - ?
Second ring - ?

Thanks for your time, it is greatly appreciated.

[bentvalves]

site:speedtalk.com piston ring end gap

cut and paste that into google and if you have any further questions, follow up here.

this topic has been beat to death already, and your ring manufacturer has some good suggestions listed on the piece of paper that came with the ring pack.

[Crew Chief]

Thanks

[engineguyBill]

Quick and easy answer:

Top ring .0045" per inch of bore diameter .0045" X 4.060" bore = .018" gap

2nd ring .0055" per inch of bore diameter .0055" x 4.060" bore = .022" gap

[KnightEngines]

I'd run .020 top & .023 second.
It'll hook well on that surface & non alcohol fuel runs hotter, a little extra is safe, won't cost any measurable power or extra blowby, may save a motor if something is not quite right & cyl temps get a bit warmer than anticipated.

[CGT]

I'd run .020 top & .023 second.
It'll hook well on that surface & non alcohol fuel runs hotter, a little extra is safe, won't cost any measurable power or extra blowby, may save a motor if something is not quite right & cyl temps get a bit warmer than anticipated.

I agree with this, a little safety margin. There just isn't anything to be gained and a lot to lose by being too tight.

[engineguyBill]

Quick and easy answer:

Top ring .0045" per inch of bore diameter .0045" X 4.060" bore = .018" gap

2nd ring .0055" per inch of bore diameter .0055" x 4.060" bore = .022" gap

These dimensions are assuming that you will be using good quality piston rings, Steel or Ductile Iron top ring and Grey Iron second rings. There are steel second rings available but they are not necessary due to the fact that the second ring does not directly operate in combustion heat nor direct compression pressure. The second ring's primary function is oil control.

[bentvalves]

evening fellas.

when talking about 2 cycle engines, where there are only 2 rings fitted to the piston of which both are identical...

does the second ring still like to see a little extra gap than the top ring?

[bentvalves]

yes to my own question - WISECO/PDFs/Manuals/RingEndGap.pdf

Applications -

Top Ring
Bore x

2nd Ring
Bore x

Dirt / ATV / Snow / PWC
.0040”
.0050”

High-Performance Street / Strip
.0045”
.0055”

Street-Moderate Turbo / Nitrous
.0050”
.0055”

Late Model Stock
.0050”
.0055”

Circle Track/Drag Race
.0055”
.0060”

Blown Race Only
.0065”
.0070”

Nitrous Race Only
.0070”
.007