oil ring gap

Bkpigs · Dec 2, 2015

Checking the ring gaps on an engine rebuild and found the oil rings to be a little too large. They overlap a few thousandths. Getting the compression rings to the correct gap is easy enough with a file in a vice but with the oil rings being so thin what do you guys prefer? Same method or nip them back with a side cutter and then file the point off? I am guessing that the oil rings need the same gap as the compression rings, right?

Steve@Advance · Dec 2, 2015

I don't like the sound of this...

Sounds like you have the wrong rings. I've never had to file rail type oil rings. The gap is not as critical
as the compression rings, and is wider than compression rings. That is what makes me think they are wrong. If
they are for the wrong bore, my fear would be that they wouldn't conform to the cylinder wall or try to twist
in the ring groove. This is not an area to be in doubt of!

I would contact the seller or the manufacturer, ask before cutting them down.

Bkpigs · Dec 2, 2015

The oil ring is the three piece style. Two rings and an expander, if that make a difference. And the rings (compression and oil) came as a set. Tomorrow I will try to check the old ones to see what the gap on them are.

Harold Melius · Dec 2, 2015

I would stop and check out if you have been given the wrong rings. Normal end gap on compression rings is going to be about 4 thousands per inch of piston diameter. Oil rings are normally more than that. It's not uncommon for rings to get mixed up by people at the parts store.

Bob · Dec 3, 2015

There's gotta be a parts mix-up.

Obviously, you can't have them overlapping, and having a real tight gap is typically not even appropriate.

Read the treatise below on how much more important it is to not have much clearance besides the rings in the ring groove vs. worrying solely about the ring end gap.

On the other hand, if filing the rings to get the correct end gap is what you really need to do you need a "piston ring filer".

GOOGLE can help you with that, about $40 and up.
Dave Reed

Dick L · Dec 3, 2015

If you bought a ring set for the engine you are rebuilding you should take them back. I bought a kit once and one pack for one cylinder was large and I took the pack back and they switched to the correct rings. The only time I file rings is on a total custom build. I have the crank ring file cutter but find a thin fine grinding wheel on a stand works faster using both hands on the rings.

David G · Dec 3, 2015

I would double check before filing.

casecollectorsc · Dec 3, 2015

I think he is talking about the thin rings with a spacer that go in the oil ring groove. Put the spacer in the groove and then the thin ring
below the spacer and then the top thin ring. They do overlap some, should be good to go. You spiral the rings on.....start one end on and
follow around.

dr sportster · Dec 3, 2015

I have never filed a rail for an oil ring . The wrong oversize rings must be the cause .

farmboy48 · Dec 3, 2015

I have never seen oil rings overlap at the ends. Usually (in my case anyhow) about an 8th to 3/8 inch end gap.

Bkpigs · Dec 3, 2015

I called the supplier today and they told me to file them down to get about .015 to .020 inch clearance. Just have to make sure absolutely no burrs are left behind. He did seem surprised to hear they were overlapping.

Bob · Dec 3, 2015

The supplier was "surprised" and you accepted that???

Without being politically correct, he blew smoke up your a$$!

oil ring gap

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