Glyco rod bearing wear
 

I had the misfortune, a year ago, to have my 2.8SS rip a piston in half on the chassis dyno. The motor had less than one hour on it. I finally got it completely torn down. The Glyco main bearings, which were coated by Calico, looked fine.

http://forums.pelicanparts.com/uploa...1401340573.jpg

The rod bearings did not.

http://forums.pelicanparts.com/uploa...1401340638.jpg

Of course, the wear pattern on the rod on the blown up hole looked uneven, and the Pauter rod was a bit twisted (but they sell singletons). But no such abnormal forces affected these bearings, and all five sets look like this. I am pretty sure, from memory and from examining where the two bearing shells abut (which seems to be where no wear at all usually occurs), they look to have had the same coating as the mains, though now basically gone.

I think someone, within the last year or so, sent in a photo of a similar mottled wear pattern. And from an engine prematurely torn down for some other reason? I don't know just what to make of it, especially since they were coated, but most of that is gone. Crank looks fine.

Because this is the 66mm crank (2.0-2.2), there is no option to use GT3 rod bearings. Leaving me wondering what to do for replacements. The plain old Glyco intermediate shaft bearings look just fine, as one would expect for less than an hours use. But these don't.

It almost looks like there was an additive in the oil...and the pattern on the rod bearings is the residue of that additive.
You say the engine sat still for a length of time before being torn down...is it possible that the suspension fliud of the additive evaporated and left what you see?
Bob

Walt, can you tell if there is material gone or is it a visual staining only? Having just used Glyco rod bearings in mine, I'm a tad worried.

Dave

Those look spooky. Is it possibly corrosion as it appears to be beneath the surface of the bearing face? If not from moisture, perhaps something acidic as more to Bob's point.

I don't think this is due to corrosion. If it were, I'd think that the main bearings (which show no signs of this) would be affected also.

It has some of the hallmarks of wear, since the dark coating material still exists at the ends of the bearing halves. Checking with bearing wear sites, I see that it is normal for the parting line area to be unaffected by most wear problems.

As best my fingernail can tell, the lighter, more gray areas are depressed below the more silver layer. The silver layer looks like the babbit. Not only is the coating gone, but one way or the other some of one or the other layer right under the coating is gone.

On its first chassis dyno run this engine had lower oil pressure than I expected based on my other engines (and it has the GT3 pump, while one other has an ordinary 3.0/3.2 pump which makes good pressure), but not scary, don't keep testing, low. I made up pressure setting adjusters, which out of the box shimmed up the pressure setting spring some, and on the final visit to the dyno, they were higher. Arguably main bearings always get better oiling? But there was no differentiation between rod bearings (other than the one which got twisted), though the center main was cross drilled. This patterning isn't characteristic of low oil pressure, is it?

I was kind of hoping I'd find one of the pressure side oil pump seals askew, as that at least would explain oiling issues. But they were all normal. And all six piston oil squirters were firmly staked in place, so no help on that mystery.

Another possibility is that the coating made the bearings too tight? My measurements of the crank told me the journals were more on the low side, and that the coating wasn't going to raise it even to a minimum clearance, much less too tight.

The Clevit/Mahle site has a picture of "overlay fatigue," which looks a lot like what you see on my bearings. They list lugging (never happened here) and detonation (don't think so, as my twin plug spark settings are fairly conservative) as potential causes, along with the bearing simply not being strong enough for the loads. Their solution is for more robust bearings.

If I can use Clevite without having to regrind the crank and buy new rods, that sounds like a good plan.

I have heard that this is a systemic problem with the current source for 911 rod bearings 2.0 through 2.7 and 3.6 engines. The quality if the current rod bearings is not sufficient for extended high RPM usage.

Walt, I'm curious how did the case hold up through this torture??

Craig

As torture goes, it wasn't bad. Since I was on the chassis dyno, the moment the smoke came out a tailpipe I got the cut it off sign (unlike on the track, where I've sometimes thought I could get back to the pits, and made things worse). While the piston was in many pieces plus the crown, and the valves in that hole were smushed, the cylinder did not break apart. It cracked, but didn't break (I had to beat it apart with a hand sledge to get it out of the spigot, though). So the wrist pin on the end of the rod didn't start sawing on the case at all. I can identify a couple of dings inside the case, but nothing to have to deal with.


Your bushings for the throughbolts held up just fine.

http://forums.pelicanparts.com/uploa...1401423067.jpg

I am left contemplating whether I'll find anyone who will purchase five fine J&E pistons, knowing what happened to the sixth. I suppose they'd be fine for a street motor if you wanted valve pockets for 52mm 993 RSR intakes, and 12 to 1 CR from a 66mm crank. Given the history of this (now superseded, I believe and hope) design, doubtless there are several batches of five out there for the same reason as I acquired mine.

Here is what Scott had to say. Sounds like it is precisely my experience here:

Hi Walt-

What you are seeing is in fact overlay fatigue and is a common problem with current Glyco rod bearings. We don’t use them in race or street engines. I have a direct replacement Clevite 77 H series bearing for part # 901 103 141 00- no need to change journal size or rods.

They are 290.00 for a set and are Calico coated . I also have them for 2.4-2.7 and soon will have them for 3.2 3.3 and 3.6

At this time the Glyco mains are fine

Scott McPherson
Automobile Associates of Canton Inc.
860-693-0278
Specializing in Porsche, Audi, VW, BMW and Mercedes with our Body Shop, Race, Restoration & Mechanical Services - Automobile Associates

Nice, now get them ordered and get back on the track! You guys be at gingerman this year?

Craig

This engine needs new pistons, one new cylinder, and one head repaired (if it can be) before it goes back together. That is going to take a while. The SC race car is plenty of fun, so that's what I ran the last two years.

I work six PCA races this year, but Gingerman isn't one of them. I got there last year, partly to check it off my list. Come up to Mosport.

Interesting topic.
Does anyone know which make and quality of bearings is delivered when ordered directly through Porsche?

Well this sure leaves me feeling all warm and fuzzy. I just got the rods for my 3.2 back from the machine shop and have a set of Glyco bearings from our host. I was looking forward to starting to put my baby back together this weekend, but now I'm not sure I want to risk running these questionable bearings. Is there any reason to believe the bearing Glyco makes for Porsche are any better? Whats the deal with Mahle/Clevite not having bearings listed for Porsche?

In trying to understand this issue a little better I've come across some info that the rest of you were probably already aware. For a given application the Porsche OE bearings are color coded for where they fall within the acceptable tolerance range. Blue for tight, Yellow for middle and Red for loose. There is some information to suggest that the aftermarket Glyco rod bearings are all on the tight end of the spectrum anticipating they would be used to rebuild a high mileage unit with some wear on the crank or been micro polished and prone to being on the low end of the spectrum. If this is true, if one were to have a crank on the large side of good and used tighter bearings with a coating....? I guess I need to open up this pack of Glycos I have and see where they spec out.

That color coding for bearings is only for GT3. The "lesser" 911 simply has one STD bearing set and any others are spec'd for undersize or oversize dimensions.

You might be right on that. What I read was although there was only one part number for "lesser" 911 bearings directly from Porsche. When you open the box you randomly find the color coded bearings. The main issue and one that I can't personally verify is the OEM Glyco bearing are consistently tight as opposed to the OE units

Cupcar confirms in post #23 what I mentioned

http://forums.pelicanparts.com/911-engine-rebuilding-forum/723158-main-bearing-alternative.html

I'm not sure what you mean by opening the box and finding randomly colored bearings. All of the Glyco OE and OEM STD 911 (regular, old 911, not actual GT3) main and rod bearings I've handled have no color markings on them.

I don't think you'll find info here that the OEM aftermarket (non Porsche dealer boxed) Glycos are consistently tight. What you'll find is that they are becoming more and more inconsistent in terms of visual quality and measurable quality in terms of consistent clearance results from journal to journal, assuming all crank journals and case bores are consistent.

As far as obtaining those red & blue marked bearings. Not an easy task. Porsche Motorsport doesn't sell those to just anybody.

Hmm. I have two sets of 2.0 glyco bearings. Both are NOS. How can I tell if they are old enough not to have these problems? Country of manufacture?

Oh boy... Wonderful. Just came across this thread by chance - reading another thread that mentioned it.
I just reassembled my crank (2.0 '69 911E) with Glyco's from our host, and getting ready to put her back in the case. I don't plan on racing - just a street car. But, even then, you sometimes rev her up pretty good. So now what? Sure don't want to put her together only to have another rod bearing go bad. But really don't want the expense and trouble of replacing the ones I just installed if not sure these indeed have an issue (would need to also replace my new rod bolts and nuts again - another $200)...