Ring gaps.....where do you guys set them and why?

[Mike T]

The last time I built my motor the ring gaps were set much tighter than most would agree with (.018 top and .016 second). The top ring was set .002 wider than the second ring which most do not agree with because of trapped gas possibly causing top ring flutter.

The specs came from a guy who has built a lot of turbo Buick motors and he said the top ring sees more heat and closes up more than the second so the gaps will be close at operating temperature. Sounds logical to me so I followed the recommendations and upon tear down (for head gaskets) everything looked fine after 10 k. The motor even ran a little hot so potential was there to "butt" the ring gaps and still all was well.

 

[fastblackracing]

Mike I have used .018 top .015 middle on 3.8 bore engines and .020 top and ..016 middle on 4.0 bore engines with very good results up to high 700's crank horsepower on our engines.
This is using the old school speed pro moly rings in a 1/16 x 1/16 x 3/16 ring pack with the top of ring groove at least .250 or more
down from the top of the piston.

I think part of the trend with with different ring gap configurations is due to newer ring tech using thinner lower radial tension rings that respond to heat and sealing different than the older rings.
The pistons that I normally use are made with a groove in the secong ring land to act as a gas accumuator to help with trapped gas. So this may be part of my success with my gaps.
A different piston ringland/design package may very well benefit from a reversed gap combination.
And as we know it really ends being about the package as a whole....in this case the piston/ring package and what works for one combo will not be the best for a different combo.

 

[Mike T]

Fastblack I always appreciate your experience and willingness to share. Their are a few guys (bison being one of them) on this board who doesn't hold back info and are always an open book of knowledge.....even willing rehash old info for the sake of getting someone less knowledgeable up to speed.

 

[Chuck Leeper]

An article I saved............

 

[Mike T]

interesting read Chuck. It would almost lead you to believe that the top and second end gaps would be the same on a supercharged engine according to the chart.

 

[bison]

.018/.020 was typical for 3.8 bore turbo up to 125hp/hole. I've run larger gaps .021/.024 and there was no real difference. There definitely isn't any power with tighter gaps on these turbo engines. Tighter gaps will help reduce blow by but the cylinder needs to stay round or the blow by vs ring gap can be thrown out the window. Most are dealing with a junk block that was never meant to be over 400hp. It's likely moving all over the place under full load. Worrying about some blow by is a waste of time

 

[Chuck Leeper]

interesting read Chuck. It would almost lead you to believe that the top and second end gaps would be the same on a supercharged engine according to the chart.