Glyco vs clevite rod bearings - with data

[KTL]

The ironic thing is that AA doesn't know Frank's background. He definitely knows what he's doing and how to measure.

I recall that one of the guys here on the forum had a problem with the AA bearings being too loose and therefore he decided to coat his original bearings at HM Elliott I believe. The one thing that concerned me about doing that was the reuse is not advisable from a bearing crush standpoint.

Do a search with the name bpu699 and the term "clearance" and you'll see he commented a lot about this

Just got my engine bearings coated...looks great

[jjeffries]

I am a lesser qualified commenter here, having rebuilt exactly one 911 engine ... 82 SC, 183 K miles, head stud induced and more of a refresh than a rebuild. I am not schooled on precision measuring, so I just ordered the original size (and retained my mains, which looked like new)

When I did my engine, on a tight budget, reading these threads caused me to purchase Genuine Porsche "GT3" rod bearings. No one seems to have mentioned those in the past few entries, unless they were the 996 P/N someone referenced. I don't remember them as being obscenely pricey. Are they still an acceptable/useful/preferred solution to this problem?

John

[stownsen914]

I bought a set of Clevite rod bearings from AA a couple months ago. I think they were like $250.

As for the hassle of building Porsche 911 engines, I can partially agree with that. I wonder though if with other marques' engines people just slap 'em together and don't worry about the hassle of taking measurements.

[ahh911]

"I recall that one of the guys here on the forum had a problem with the AA bearings being too loose and therefore he decided to coat his original bearings at HM Elliott I believe. The one thing that concerned me about doing that was the reuse is not advisable from a bearing crush standpoint."

Kevin, if the bearings are returned to their original rods, is it then ok? Seeing how the bearings get crushed anyway when testing fitment or in some cars (m3) 3 full angle torques for install with full back off in between the 3 tightenings. I don't plan on re-using but just a general question.

Also, if anyone has any new info and repeating John's question, is it still advisable to use the 996GT3 standard rod bearings in the 911sc?
From what I've been told and read, they are "exact" dimensions? (Thickness included)
Phil

[Glenfield]

Agree that this would be interesting to know. I am currently going with clevite bc it was what my engine builder recommended as a substitute for SA Glyco. Also going Porsche dealer main bearings which are almost as expensive as 1 share in Tesla!

Originally Posted by jjeffries

I am a lesser qualified commenter here, having rebuilt exactly one 911 engine ... 82 SC, 183 K miles, head stud induced and more of a refresh than a rebuild. I am not schooled on precision measuring, so I just ordered the original size (and retained my mains, which looked like new)

When I did my engine, on a tight budget, reading these threads caused me to purchase Genuine Porsche "GT3" rod bearings. No one seems to have mentioned those in the past few entries, unless they were the 996 P/N someone referenced. I don't remember them as being obscenely pricey. Are they still an acceptable/useful/preferred solution to this problem?

John

[KTL]

Well i think the crush thing is debatable. I remember chris_seven (RIP, fine sir...... ) mentioning that this is a subject of debate he encountered many times. But I also wonder about the spring-effect of the bearings when they're reused. I think over time bearings can lose their "grip" in the bearing bore and not fit as tightly as intended. But that's just observation on my part. I've not built a ton of engines so I don't have any technical knowledge about how much spring is needed to keep bearings from spinning in their bores.

I agree that you have to crush the bearings and then disassemble the rods after you've assembled them for measuring. I think it's when the engine is put into operation and the rods and mains are stressed that the crush becomes an issue? A lot of people have reused bearings on these engines over the years so I wouldn't hesitate to use them if they're in good shape. And yes, definitely keep the bearings shells with the rods they came from. Make sure the shells go back in the same part of the rod they originated from.

The 996 GT3 bearings haven't been discussed on this particular thread because the AA Clevite bearings have not been made for the 3.0L rod size. Yes they're not terribly expensive if you get them at wholesale price. I think I paid about $20 per each shell (that means you need 12, not 6) when I bought them for my racecar rebuild. Recently sold them for $200. They're very nice quality with clear indication of quality control measuring on them

Various Engine Parts- 3.0L/3.2L/3.3L (and others?)

They are a different dimension than the 3.2/3.3/3.6 rod bearings in this discussion. I recall, but haven't checked recently, that AA sourced the Clevite bearings for 2.7 and 3.2/3.3/3.6 rods because those were the suspect Glyco bearings. I don't see that AA is making the Clevite bearings for the 3.0L rod since they were never a problem. But I bought some Glyco aftermarket 3.0L bearings that were made in the same time and location as the bad 3.2 bearings and couldn't risk using them. So they're junk and money down the crapper since I sat on them far too long to be able to return them to Pelican. Shame on me.......

I don't doubt what stownsen914 is saying. A lot of people assembling domestic engines just take their chances on STD being STD and they don't worry about the clearances simply out of ignorance. I think its a shame that we pay a premium for these old tech bearings and get poor quality. But I suspect that's just a matter of numbers/economies of scale? There's a lot bigger market for domestic bearings than there is for these old airplane engines

[burgermeister]

Some more information, some crow eating, some interesting measurement artifacts ...

In the past week I have ordered and received a few very nice Mitutoyo digital micrometers to replace my Mitutoyo-knockoff Chinese vernier micrometers (which I did calibrate to a nearby value with shop grade gage blocks). I also got a very nice Mitutoyo tenths reading bore gauge.

Rechecking everything. The crank is again right on the fat end of the spec. The rod bores are all right between the (tight end) and the (tight end +0.0004") of their spec - so well within spec, just not all of them are right at the tight end. Rod bolts were tightened with a stretch gauge to .010.

The old bearings measure .0003 - .0004 thinner than the AA bearings.

So I checked clearance to the crank journal with the old bearing shells, using 2 that measured identical and had no visible wear. I came up with .0022 - right on the money.

I then checked the same rod with the AA bearings. I came up with .0023 - also right on the money. But wait - they measured thicker. And they are supposed to be thicker! I conclude that the coating is soft, and is readily deformed by the bore gauge, but not by the micrometer.

This poses an interesting question - what is the actual clearance???



And as to eating crow (yum! not the first time, won't be the last) - my measurements were wrong. Kevin, thanks for the kudos, but it was apparently misplaced. Using chinese cheapo tools to measure to the tenth is fraught with peril.

The one rod checked with the new tools, at .0023, would seem to have .0015 clearance even if the bore gauge deformed all of the coating, even if the coating is .0004 thick on both shells, and this is in spec (though at the very tight end of it). I have not yet checked any more of them, and it will need to wait a month as the engine time is coming to a halt for a while. Also I have bigger fish to fry with the case...

So AA was not wrong when they told me my measurements were wrong. I attribute it to measurement error stackup. A few tenths over 4 measurements does add up. And the plastigage - well, it read .001, but asking .0005 accuracy from it may be expecting too much as well, especially when the cap needs to be tapped off the rod to get it off the crank.


A note on the Mitutoyo-knockoff vernier micrometers I previously used. They have screw error of .0002 - .0003 over a pretty short distance. It never seems to amount to much more than that even over the full range, but the error is variable and can show up in little travel, so calibrating with gage blocks does not turn them into super precision instruments. I was a bit too clever figuring (wrongly) that error would add linearly with travel. Reading the vernier is also a little subjective. So, given their price (less than 1/10th of the actual Mitutoyos), they are pretty darn good, but measuring to the .0001 is asking a bit much of them.

[Walt Fricke]

Digital micrometers can also be inexpensive. Mine (I have several), like my digital dial indicators, measure to half a 10,000th (0.00X0 or 0.00X5). They seem to measure, within these limits, consistently, and agree with each other. Within their limits, might they be accurate enough when looking at only three decimal places?

Glad to hear we weren't placing our faith in the wrong bearings, though.

[gsxrken]

Originally Posted by KTL

Well i think the crush thing is debatable. I remember chris_seven (RIP, fine sir...... ) mentioning that this is a subject of debate he encountered many times.

That is unwelcome tidings. I have missed his incredible metallurgy contributions and within the last month realized I hadn’t seen him weigh in. Just damn.

[rudedude]

I hate to bump old threads but I am wondering if the rod bearing controversy continues.
The picture I have is of a set for a 2.4 I am building and wasn't aware of an issue until I unpackaged and looked at these new glyco bearings from a reputable supplier. They are giving me a hard time as I wonder what kind of quality control they have. I would be interested if anyone would use bearings that look like this.
Thanks,
Jule

[Walt Fricke]

The supplier won't swap out the one with the incomplete coating?

Have you done the measurements others have done? Other than the one, are they all the same thickness at the points you measure?

[dannobee]

No, I wouldn't run them. Both the coating defect and the crush height defect on the bearing shell to the left of the one with the coating defect. And the shell to the left of that one.

I"m not big on King bearings, but they do have a decent explanation of bearing crush.

https://kingbearings.com/wp-content/uploads/2014/10/Design-of-crush-height-for-reliable-press-fit-of-high-performance-bearings.pdf

Glyco has had problems with QA in the South Africa plant for awhile. Or it could be that they produced a lot of bearings before the world caught on to the problem and there's still quite a few in the pipeline. Do the boxes list the country of origin?

[rudedude]

I hadn't read this thread before I bought the bearings but after looking at the glyco bearings and their lack of quality control I found this thread. The supplier is getting me a new set as I don't think they will refund my money 3 months after I bought them. They appear to have been produced in 2019 if that is the stamping on the back and measure to within .0003" of the glyco that were in the motor that were made in 1987. The only reason it is apart is the myriad of leaks from the previous rebuild that used some type of silicone sealer everywhere. I have ordered new clevite from one of the suppliers mentioned.
Thanks for the help and I hope this helps someone else.
Jule

[LukasM]

Has anybody received a set of Glyco bearings in 2023 or 2022, did they finally manage to sort out the QC problems that the non-German made bearings seem to have?

[stownsen914]

After all the bad news, I wouldn't use Glyco rod bearings in my engine tbh. I've heard mains are less of a concern than rod bearings. I bought the AA Clevite rod bearings.

[Dpmulvan]

Originally Posted by KTL

Well i think the crush thing is debatable. I remember chris_seven (RIP, fine sir...... ) mentioning that this is a subject of debate he encountered many times. But I also wonder about the spring-effect of the bearings when they're reused. I think over time bearings can lose their "grip" in the bearing bore and not fit as tightly as intended. But that's just observation on my part. I've not built a ton of engines so I don't have any technical knowledge about how much spring is needed to keep bearings from spinning in their bores.

I agree that you have to crush the bearings and then disassemble the rods after you've assembled them for measuring. I think it's when the engine is put into operation and the rods and mains are stressed that the crush becomes an issue? A lot of people have reused bearings on these engines over the years so I wouldn't hesitate to use them if they're in good shape. And yes, definitely keep the bearings shells with the rods they came from. Make sure the shells go back in the same part of the rod they originated from.

The 996 GT3 bearings haven't been discussed on this particular thread because the AA Clevite bearings have not been made for the 3.0L rod size. Yes they're not terribly expensive if you get them at wholesale price. I think I paid about $20 per each shell (that means you need 12, not 6) when I bought them for my racecar rebuild. Recently sold them for $200. They're very nice quality with clear indication of quality control measuring on them

Various Engine Parts- 3.0L/3.2L/3.3L (and others?)

They are a different dimension than the 3.2/3.3/3.6 rod bearings in this discussion. I recall, but haven't checked recently, that AA sourced the Clevite bearings for 2.7 and 3.2/3.3/3.6 rods because those were the suspect Glyco bearings. I don't see that AA is making the Clevite bearings for the 3.0L rod since they were never a problem. But I bought some Glyco aftermarket 3.0L bearings that were made in the same time and location as the bad 3.2 bearings and couldn't risk using them. So they're junk and money down the crapper since I sat on them far too long to be able to return them to Pelican. Shame on me.......

I don't doubt what stownsen914 is saying. A lot of people assembling domestic engines just take their chances on STD being STD and they don't worry about the clearances simply out of ignorance. I think its a shame that we pay a premium for these old tech bearings and get poor quality. But I suspect that's just a matter of numbers/economies of scale? There's a lot bigger market for domestic bearings than there is for these old airplane engines

Clevite does indeed make rod bearings for 3.0 rods, I have a set.

[Dpmulvan]

Originally Posted by stownsen914

After all the bad news, I wouldn't use Glyco rod bearings in my engine tbh. I've heard mains are less of a concern than rod bearings. I bought the AA Clevite rod bearings.

That’s what I remember as well, it was rod bearing failure not mains. However people building 3.0 where using gt3 main bearings from Porsche about $600 retail.

[LukasM]

Originally Posted by Dpmulvan

That’s what I remember as well, it was rod bearing failure not mains. However people building 3.0 where using gt3 main bearings from Porsche about $600 retail.

They are actually quite a bit cheaper, $28 each per shell half so $336 for the set.

https://www.pelicanparts.com/More_Info/99610312194.htm?pn=996-103-121-94-OEM

So about the same price as Mahle Clevite. I haven't read about any comparisons in terms of longevity, but would tend to think that Clevite with their latest tech tri-metal (Calico?) coating would be better than Porsche OEM, where you are paying for Glyco shells that have been pre-checked (and maybe manufactured in Germany vs. Easterns Europe oder third world country)?

Would love to hear our experienced engine builders that have seen both of them up close, e.g. from race engines that see a lot of stress.

[mikedsilva]

I know it's not related to the title of this thread, but perhaps try ACL bearings.
ACL bearings are made in Australia... and they come in a STD side and also an HX which is extra clearance (an extra thou overall). https://www.aclperformance.com.au/

I have used them in several builds now.
Locally, they work out to approx 180AUD (or 120usd) a set.

[PeteKz]

Originally Posted by LukasM

They are actually quite a bit cheaper, $28 each per shell half so $336 for the set.

https://www.pelicanparts.com/More_Info/99610312194.htm?pn=996-103-121-94-OEM

So about the same price as Mahle Clevite. I haven't read about any comparisons in terms of longevity, but would tend to think that Clevite with their latest tech tri-metal (Calico?) coating would be better than Porsche OEM, where you are paying for Glyco shells that have been pre-checked (and maybe manufactured in Germany vs. Easterns Europe oder third world country)?

Would love to hear our experienced engine builders that have seen both of them up close, e.g. from race engines that see a lot of stress.

When I built my 3.2 engine two years ago, William Knight warned me away from Glyco's and strongly recommended the Clevite. That was before I saw this thread. Glad I took his advice.