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Old 10-03-2018, 06:11 PM   #1 (permalink)
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To hone, or not to hone, on re-ring?

Hello all,

Been chasing something kind of elusive, that is very likely to get a bunch of people saying it's total hooey. Doesn't belong in the Unicorn Corral, though, because there's some evidence. I just can't find the *original* source.

Ok, so I've got this old Explorer with ~160k miles on the OHV Cologne V6. The spare truck has about the same, on the same engine. The plan is to pull the spare engine and refurbish it - basically clean it off, new seals, etc. Nothing fancy. It isn't that much more money in parts to do a full rebuild. Trouble is, the cost of the machine work on the block makes it non-economical for a "cheap project".

So I started poking around looking for how to re-ring the engine, found the conventional wisdom about "breaking the glaze", dingle-ball hones, etc.

Then I found this: Careful with that hone, Eugene!

Basic premise: The engine has already reached the best possible surface finish for the rings against the cylinder bores, by running itself in. There's no such thing as a "glaze" in most engines.

Why would you mess with that, if the cylinders are still round/straight and show no signs of scuffing, nor a ridge?

It mentioned "reprints of articles covering actual lab research done by the SAE - Society of Automotive Engineers - to support these claims". The article was first written in 1999, and was a story about a class the author took "a number of years ago".

I cannot find those papers, and it is driving me up the wall!

I did find a lot of info about "Plateau honing".

Basic gist: it is the goal of a ring/cylinder pair to achieve a "Plateau" surface condition, where you have the cross-hatch pattern for oil holding, with smooth surfaces between the cross-hatch, on the cylinder bores. Your engine does this by running in, rubbing the rings on the cylinders. Most of the wear happens in the first hour, and it levels out at about 24 hours of running. Assuming no catastrophic issues, or other problems, you are left with the optimal surface finish on the bores.

Further searching found lots of anecdata about "certain manufacturer's recommendation to not hone when installing their rings". I found a source document for that: ACL Re-Ringing and Honing

Basic gist: An amateur doing a hone job is more likely than not to either get the wrong surface finish or to leave grit in the bores/engine, leading to early ring failure (and/or other worn-out engine parts in the case of excess grit) and a warranty claim. So the ring manufacturers just say "don't hone", as the odds are, you're more likely to get a good engine that way.

Seems legit, but has nothing to back it up in terms of "you'll get a better ring seal that way".

If you search around a bunch, you run across large marine diesel engine manufacturer tech bulletins, aircraft engine tech bulletins, GM LS engine tech bulletins, etc. that either mention re-ringing a non-honed cylinder, recommending not honing the cylinder unless it is damaged, or explicitly disallowing honing of the cylinder (in the case of the GM LS engine only the second ring was being replaced, and GM would not pay for any machine work, nor warranty said work, unless there was other damage that needed correcting.)

There's a lot of info from the Flex Hone company, with a ton of detail about the desired surface finish. Here are two pdf's:

Brush Research PDF 1

Brush Research PDF 2

In the second one, in particular, they basically lay out the case that the cylinder bore surface finish that an engine arrives at through proper break-in is the desired finish for a new engine, though they don't exactly say so outright, IIRC. They claim that their Flex Hone tools will produce that finish, of course.

So, can anyone else find those SAE papers about ring vs. cylinder surface finish, break-in period, etc. that concluded you should not do a "glaze breaker hone", contrary to all received wisdom to the contrary outside of the usual "I got away with it on an old engine I redid as a poor kid in my dirt-floor garage, ran great!" anecdotal stuff?

It's so tantalizing. The SEM micrographs, the friction research, the stuff about Plateau honing, all that points in the direction that the first article suggests: absent any damage/excessive wear, if the cross-hatch pattern is there, don't hone. Just toss in new rings, it'll break-in just fine relying on wearing the rings to match the cylinders, with the cylinders being worn a lot less this time around.

Sounds too good to be true. I want those SAE papers, and I cannot find them. Plenty of papers on how the break-in process happens, plenty of stuff on new ring tech, new honing tech, new cylinder liner tech, etc. Just not a specific study on run-in bores vs. honed/bored bores, etc. and their effect on break-in with new piston rings.

There's a lot of good info-diggers here on Ecomodder. What can y'all find?

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