Piston ring gap range

I first did #1 with a virgin hone, which left streaks as you can see. But then the hone collected buildup/residue from the sleeves on the grit pads so the subsequent cylinders didn't get streaks although did get cleaned. The buildup on the pads looked greasy and kind of like buildup on sandpaper after sanding

Not much but this is my throwaway vehicle that I am using for education/fun purposes, whenever I have time.

 

Stop using your "leakdown test" as a baseline. You weren't even close to doing it right.

PS that Hone job doesn't look right.

 

I confirmed the air was escaping through the pistons when I took the oil pan off -- by both feeling the air coming out with my hand and using a 1/2" thin electrical conduit pipe meaneuvred through the crankcase as a stethoscope -- not through the gasket, not through the valves. And the gap in the rings exceeded the threshold, which further confirms the theory.

 

I did and filed them to the spec range. But I noticed that the oil expander, while it's supposed to compress like an accordion, doesn't always do that and something the ends overlap, obstructing the seat of the side rails. Do you think I should just leave it as is, or clip it like 1-2 mm with electrical angle pliers, to avoid overlapping ends?

 

It’s been a long time since I built an engine. And that was a 350 and a 383 stroker. Chevy
The oil rings did NOT over lap.

I did research the subject a bit for you.
And everything says, NO overlapping.
And the actual way the it meets is important too.
They need to meet in a M or W.

See these links for references.
https://www.us.mahle.com/media/usa/motorsports/mms-ring-instructions-7-8-20.pdf
https://www.enginelabs.com/engine-t...vealing-the-secrets-of-the-oil-control-rings/

 

@TnShooter -- someone is telling me I should use oversized rings ONLY with oversized pistons and not in my application where I am using standard pistons with slightly worn cylinder sleeves, even when filed down to a correct gap size. Is that true? In that case, I need to either bore my sleeves and get new oversized pistons OR revert to the standard rings and how that the spec deviation is not causing too much leak.

 

What size rings did you get .010?

 

0.50 mm oversize: https://www.rockauto.com/en/moreinfo.php?pk=5544888&cc=1434686&pt=5640&jsn=8

the spec on that page reports the same diameter for both STD and oversized, which is why I thought the geometry would still fit in the hole the same way (OS only having more slack to file down)

 

You really need to mic the bore and go according to those results.

.5mm is about .020 that’s a lot. You typically run those rings when the cylinder has been bored.
I’d probably stick with the standard rings. The last thing you want to do is score the bore by using the wrong size rings.

 

That seems reasonable, under the assumption that the OS rings are also of a bigger diameter, which I am not sure and will try calling the manufacturer. The RockAuto specification page (which may be incomplete) does not report a different diameter for STD and OS, which was giving me the impression just filing down OS to spec may be alright.

 

Yeah. Rings are almost always marked with the standard bore diameter and then +.020, .030 ect.
You have to do the math. That’s just the way it’s always been done.

 

So in other words, the diameter on OS will most likely be larger as well and the seal will not be proper?

But given that the standard rings are just mildly out of range (meaning the sleeve W&T is relatively minimal), using STD out of the box is a better bet for a better seal than monkeying around with OS rings, which won't fit correctly even when filed down to spec?

 

That’s what I do. I wound try to make the oversized rings fit.
I stick to STD rings.

 

Sounds perfectly reasonable.

 

@TnShooter -- however, what is slightly confusing is that PartsHawk does have separate pages for STD and OS but both specify the same attributes, notably diameter, which could then support the filing down OS approach. I sent an email to Enginetech to inquire. It is possible that the specs are different and that the PartsHawk OS page incorrectly reports the STD metrics.

 

The company replied: "These piston rings come pre-gapped, and the standard is sized to fit a standard bore, while the .50 is sized to fit a .50 oversized bore. We do not recommend any file to fit on these rings. "