I was just thinking about this tonight and brought a question up. I have my rings gapped right now to the min. requirement from Wiseco on a .020 overbore. I plan on running 15+lbs of boost on it and was wondering if I need to make them have more of a gap. I have always been taught to build tight motors but is that too tight.(I will update with specs tomorrow, their at work) I also don't want to gap them too much because of blow by. What should I do?

Your top ring should be gapped slightly larger than spec. The second ring will be gapped to spec. This is of course because your building a turbo motor. N/A you would follow spec.

But the spec on the ring gap is a window. I gaped them at the tightest spec. I will pull the piston and regap the top ring though. Thanks.

Ok, I called Wiseco again and they told me 5 thousandths(.005). I checked my gap on the top ring and came out with .015.... I think I need new rings.

Originally posted by Slo2g
Ok, I called Wiseco again and they told me 5 thousandths(.005). I checked my gap on the top ring and came out with .015.... I think I need new rings.

.005" sounds more like the piston-to-wall clearance. .015" is really tight, stock spec for the top ring is like .020" or .022".

Yeah I called back and he said .005 per inch of bore. He said I need to roughly have on the top ring .017 and bottom ring at .019.

Originally posted by Slo2g
Yeah I called back and he said .005 per inch of bore. He said I need to roughly have on the top ring .017 and bottom ring at .019.

Yep.... that's right... 0.005" per inch of bore.

0.005" x 3.465" = 0.0173"

With those pistons, I would gap them in the 0.017-0.018 range for sure. 0.020" is a little too much for a moderate boost street engine (IMO).

Many machine shops in our area disagree with you doug. I went through this with the 2.4L when I checked the gaps before assy.

Originally posted by Star Turbo Talon
Many machine shops in our area disagree with you doug. I went through this with the 2.4L when I checked the gaps before assy.

Disagree with me about what? What do piston ring end gaps have to do with the machine shop? I'm not sure what your machine shops told you, but you should have checked with your piston and ring manufacturer regarding the ring end gaps.

If you're saying that a ring end gap of 0.020-0.022 will work and the engine will operate fine, then I'd say that's a correct statement. If you're saying that large of a gap is optimal for reducing blow-by and increasing horsepower, then I'd disagree. But I say go for it if you think that works for you and your setup. Lot of factors come into play with determining proper gaps. When building a performance engine, you want to keep the end gap as tight as you possibly can get away with. Gapping them a little more open will also work fine, but may not be optimal.

On a side note, I wouldn't gap the top ring any larger than the bottom. For a boosted street motor, I would actually go a little less on the top ring.

To each his own, I guess.

No the arguement is the top ring gap is slightly larger than spec on a boosted motor due to the increased heat that the top ring will see. The top ring should never be compared to the bottom ring. the bottom ring is for Oil control. I thought that was obviously the discussion. I tend to follow builders that spend a living building race engines than someone who makes it a hobby.

I agree with both of you on that but I will go with about .017 on top and .019 on bottom. I agree that I want them as tight as possible on a street application but all race would be slightly larger. Thanks for the help guys.

Originally posted by Star Turbo Talon
No the arguement is the top ring gap is slightly larger than spec on a boosted motor due to the increased heat that the top ring will see. The top ring should never be compared to the bottom ring. the bottom ring is for Oil control. I thought that was obviously the discussion. I tend to follow builders that spend a living building race engines than someone who makes it a hobby.

Sorry, I should've used different terminology. I was mostly referring to the top and 2nd compression rings... not the bottom, or any, of oil rings.

I would agree that gapping the top compression ring slightly larger than the stock spec, or larger than the spec for a non-boosted motor, is a good idea. I still think 0.020-0.022 gaps for JE and Wiseco pistons/rings are a little on the larger side for a street turbo setup.

Good discussion here... I love to see topics a little more advanced on 2GNT. :)