Ring gap
 

Thought I'd ask this in it's own thread in case it is an issue for others. I'll be pushing 12lbs max from my S/C.

I now have tried 2 sets of rings in my motor. The end gaps right out of the box are as follows:

1. Mahle (Perfect Circle) 1st ring .018 to .019 2nd ring .019 to .026

2. Sealed Power 1st .019 2nd .020 to .025

Mahle says 1st should be .019 (luck on that I guess) but 2nd should be .015!

Sealed Power ((Speed Pro) says 1st & 2nd ring should be .019 on S/C motors

What would you do here?

My understanding is that the second ring gap is supposed to be slightly (like 10-20%) larger than the top ring, but I'm a long way from an expert on the topic.

--Ian

If I interpret the manual correctly, that is for high pony drag race applications while boosted rings are recommended to be the same...

Speed Pro Top Rings
(ductile iron, 4" bore) 4.000" Example Minimum Gap Factor
Moderate Performance .016 -.018 (.004 per inch of bore diameter)
Drag Racing, Oval Track .018 -.020 (.0045 per inch of bore diameter)
Nitrous Oxide -Street .020 -.022 (.005 per inch o f bore diameter)
Nitrous Oxide -Drag .028 -.030 (.007 per inch of bore diameter)
Supercharged .024 -.026 (.006 per inch of bore diameter)


Speed Pro 2nd Rings
(cast Iron, 4" bore) 4.000" Example Minimum Gap Factor
Moderate Performance .020 -.022 (.005 per inch of bore diameter)
Drag Racing, Oval Track .022 -.024 (.0055 per inch of bore diameter)
Nitrous Oxide -Street .024 -.026 (.006 per inch of bore diameter)
Nitrous Oxide -Drag .028 -.030 (.007 per inch of bore diameter)
Supercharged .024 -.026 (.006 per inch of bore diameter)


Notice: Most of the second ring gap recommendations are larger than the top rings. Recent testing has proven that a
larger second gap increases the top ring's ability to seal combustion. This larger "escape" path prevents inter-ring
pressure from building up and lifting the top ring off the piston allowing combustion to get by. Many engine builders
have reported lower blow -by and horsepower gains at the upper RPM ranges with wider second ring gaps. Also,
almo st every new car made is using this inter -ring pressure reduction method to lower blow -by and emissions and to
increase engine output.

Both Supertech and Wiseco recommend a 2nd ring that is several thousandths of an inch larger than the top gap. The idea is to avoid pressure build-up on the bottom side of the top ring.

I suspect "Supercharged" in this context means methanol/alcohol-fueled pro-stock cars. Our engines are quite tame compared to some of the stuff they sell rings for.

Yeah you're definitely in the "moderate performance" category. Also our bore is closer to 3.3" instead of 4" assumed in those specs.

Thanks guys I had decided to go with them as is but I needed to hear it from someone else. I'm like a girl that way.

My big curiosity is different concepts between brands but in practice measured the same. Kinda wish I'd of slapped in the first set and saved $50 and a week. :slap:

Anyway I bolted the bottom end together tonight. It feels good to spin the assembly around in the block and have it all moving smooth as buttah.

Oil clearances all marked on the caps.

https://lh6.googleusercontent.com/-S...o/DSC_2775.JPG

https://lh3.googleusercontent.com/-O...o/DSC_2776.JPG