polishing piston rings?

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Belgian1979
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polishing piston rings?

Post by Belgian1979 »

A question that came to mind when building my current engine.
For the actual engine in my car I followed the recommendations in D. Vizards book SBC Pistons, rods & crankshafts on page 67 where he advises to lightly stone the edges of piston rings and then polish them with crocus cloth. So what I did at the time was run the stone once over the sharp edge of the rings and then go over it with a crocus cloth to lightly polish them.
It is said to aid in breaking in of the rings.

Now I wonder if that could have actually hurt with things like the second ring oil control. I have good compression btw (ca. 180)
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Re: polishing piston rings?

Post by mag2555 »

The rolling over of the 4 corners at each end of all the rings, and yes! all the rings including the oil rail rings is done so that the 4 outside corners do not dig into the cylinder wall and scratch them and also so that they spin free’er around the ring groove as they all need to do, and while spinning they do not chew up the outside top or bottom of the ring groove.

On the inside 4 corners of a ring the same thing is done, but of course these 4 corners can not scratch up the cylinder wall but the can hang up a ring from spinning and or chew out the rear of the ring groove.

Another very critical thing with Moly face rings that you gap is the if you file them to the needed gap you only make cuts pushing the file in towards the center of the ring.
Doing a back & forth saw type motion can flake off the Moly face of the ring at the intersection of the end of the face of the ring and the gap.

No Moly face where the ring contacts the cylinder wall will cause rapid ware of that spot of the face of the ring.

A very fine soap stone is what I have always used to do a combo of rolling over and polishing these sharp corners, or I have used a 1/4” shank pan cake stone, one of the very fine grit gray colored ones to do the job also at times.


I thin the edges of these stones out a lot by running them against my bench grinder which makes it easier to use them.

If I feel I need a smoother surface then the rework that the stone leaves then I use 320 grit wet or dry sand paper folded over the blade of a single edge rasor.
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Re: polishing piston rings?

Post by BillK »

Nothing against Dave but a LOT has changed in piston ring technology in the 30 years since that book was originally published. Other than breaking the corners at the gap like Mag said I pretty much leave rings alone. For that purpose I use a very fine stone but also have a couple of Revlon diamond nail files that work great for this and many other purposes :)

It would be interesting if you would call the ring manufacturer and see what they suggest.
Bill Koustenis
Advanced Automotive Machine
Waldorf Md

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mag2555
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Re: polishing piston rings?

Post by mag2555 »

Also you will have a smile on your face when you see how much easier the pistons & rings load into the bore when the corners are Nicely rounded over!
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
Belgian1979
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Re: polishing piston rings?

Post by Belgian1979 »

Well rings are rings. Don't think much has changed in ring technology in the past 30 years, but would like to get views on this. So far it seems it won't hurt but may not be needed.
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Re: polishing piston rings?

Post by allencr267 »

The circumference, top & bottom? Never!
Those 4 corners & edges on each end just like mag2555 says, always.
No gouged lands during install and doesn't scrape away lands while running.
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Re: polishing piston rings?

Post by hoffman900 »

Belgian1979 wrote: Sat Nov 13, 2021 10:57 am Well rings are rings. Don't think much has changed in ring technology in the past 30 years, but would like to get views on this. So far it seems it won't hurt but may not be needed.
Not even close.
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Re: polishing piston rings?

Post by lefty o »

huge advancements in rings over the last 30 years.
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Re: polishing piston rings?

Post by PackardV8 »

lefty o wrote: Sat Nov 13, 2021 12:14 pm huge advancements in rings over the last 30 years.
Of all the parts one handles during a long block assembly, rings may have changed more than any other part; thinner, better materials, better profiles, better finish.
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Re: polishing piston rings?

Post by Belgian1979 »

Image
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Re: polishing piston rings?

Post by Roundybout »

Other than the gap and smoothing the edges at the gap, I don’t do anything with them other than checking and verifying. A good magnifying glass looking for nicks, scratches or gouges. Clearances in the ring groove and so on. Materials, finishing, profiles ect. are all engineered into the ring. 30 years ago rings were thicker, bore finishes different, materials and oil for example and this prep may have been needed. Not so much these days.
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Re: polishing piston rings?

Post by Belgian1979 »

Ok, but would it hurt?
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Re: polishing piston rings?

Post by PackardV8 »

Belgian1979 wrote: Sat Nov 13, 2021 2:36 pm Ok, but would it hurt?
Imagine trying to hand bevel today's .8mm rings. They're difficult enough to load and install without damaging them.

The old 5/64" and 1/8" cast iron rings on our obsolete engines had their own problems, being brittle was one of them, but it was no problem to file fit and bevel if necessar difficult to damage them.
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Belgian1979
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Re: polishing piston rings?

Post by Belgian1979 »

PackardV8 wrote: Sat Nov 13, 2021 4:05 pm
Belgian1979 wrote: Sat Nov 13, 2021 2:36 pm Ok, but would it hurt?
Imagine trying to hand bevel today's .8mm rings. They're difficult enough to load and install without damaging them.

The old 5/64" and 1/8" cast iron rings on our obsolete engines had their own problems, being brittle was one of them, but it was no problem to file fit and bevel if necessar difficult to damage them.
Don't remember how thick they were but the pistons were CP. I don't think .8 mm.
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Re: polishing piston rings?

Post by BillK »

Belgian1979 wrote: Sat Nov 13, 2021 2:36 pm Ok, but would it hurt?
It could very well ruin them but the only one that knows is the ring manufacturer. I trust them to make the rings pretty much ready to install. When we have to file fit them it affects the ends but other than that I say leave them alone.
Bill Koustenis
Advanced Automotive Machine
Waldorf Md

www.enginerepairshop.com
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