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Ring gap - should I worry...

This has probably been discussed already but I'm not having much luck with the search function so I'll risk digging it up again...

I have a 3.2 rebuild in progress and I'm setting the ring gap for my brand new 98mm JE pistons/bored and re-plated cylinders. I've got the gap on the compression rings to .015", but when I closely inspected the edge of the ring where I filed it (using one of the less expensive benchtop ring grinders) I noticed that it was not perfectly square. I can rotate a straight edge back and forth slightly and see a bit of a gap towards the inner edge of the ring.
One in particular is probably .016" on the inner edge.

Should I not worry and leave as is, or try and take them up to .016" and get them square, or spend the $150 and get another set of rings?
They started of at .012" which is too tight according to people I checked with and the JE spec. The JE spec sheet says I can go to .017" but most people I talked with recommended .015".

Is there any particular secret to getting one of these inexpensive ring grinders to get a nice square edge?

https://www.summitracing.com/parts/pro-66785/overview/

Thanks as always for any help/suggestions.

Bill


Last edited by wjdunham; 05-20-2019 at 01:02 PM..
Old 05-20-2019, 12:55 PM
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Doesn't need to be parallel perfection there IMO. Make sure you're setting gap at the tightest point and do your best at being parallel. I use a cutoff wheel in my vice to cut my rings and then hand file/debur manually. I'm usually cutting a lot of material from my rings and the old style manual wheel ring files would take hours. Opinions will vary.

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Old 05-20-2019, 02:10 PM
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Porsche gapped the 82-83 top ring at .008-0.016”

I ran .008-0.009”. No issues.

Last edited by VFR750; 05-20-2019 at 02:58 PM..
Old 05-20-2019, 02:55 PM
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JE spec is for water cooled engines.

Air cooled cylinders expand more. I followed Porsche’s gaps.

Rings from Total Seal showed up, at the min spec. No trimming was needed.
Old 05-20-2019, 03:00 PM
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ring gap

You are ok at that spec.Total Seal rings work well but take longer to seat so leave the non detergent oil in a little longer before doing leakdown test.For reference used motors at 5% or more leakdown the ring gaps are getting close to 1mm which is the wear limit.After 5% the blowby past the rings is preheating the precious oil you need to cool the motor.Ciao Fred
Old 05-20-2019, 03:52 PM
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Quote:
Originally Posted by faapgar View Post
You are ok at that spec.Total Seal rings work well but take longer to seat so leave the non detergent oil in a little longer before doing leakdown test.For reference used motors at 5% or more leakdown the ring gaps are getting close to 1mm which is the wear limit.After 5% the blowby past the rings is preheating the precious oil you need to cool the motor.Ciao Fred
Which spec. are you referring to here when you say "You are ok at that spec."?

Now I'm thinking that I should get a new set of rings and not touch them if they are greater than .008"?

Bill
Old 05-20-2019, 04:00 PM
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I would follow the maker of the pistons specs , JE knows that the pistons were made for an air cooled porsche . Call them if you are in doubt
stick to the plan
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Old 05-20-2019, 08:44 PM
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J.E. recommendation is for a cast iron block...
Mahle ring gap is for a Ductile iron top ring...different materials have different expansion rates...this includes rings.

My personal experience is no less than .013 gap on top ring for a 90mm nikasil cylinder. I did a high compression build and saw the beginning of rings butting together. This is for the rings that J.E. and CP supplies.
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Old 05-21-2019, 01:06 PM
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I wouldn't worry about slight out-of-squareness on ring ends - not an issue. What is more important is running a slightly larger gap on the second compression ring - this helps reduce oil consumption. Only .002" larger than the top ring gap clearance can make a surprising difference.
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Old 05-24-2019, 01:29 PM
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I wouldn't worry about slight out-of-squareness on ring ends - not an issue. What is more important is running a slightly larger gap on the second compression ring - this helps reduce oil consumption. Only .002" larger than the top ring gap clearance can make a surprising difference.
Following the JE recommendations, I'm trying to get to .015" for the top compression and .017" on the 2nd ring - so yes, planning .002" larger.
Old 05-24-2019, 05:17 PM
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I'll throw this out there, if your gap is too tight, even Nikasil will be damaged (my cylinders were scored after about 5 years of running).

BTDT. I will ALWAYS go looser than tighter, but I am boosted.

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Old 05-29-2019, 07:35 AM
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