New Glyco mainin bearings 1.5 thou too loose

[kamaro]

I have decided to refresh my '87 Carrera 3.2 engine, just a typical rebuild, nothing fancy, and after 180,000 miles it must be due for that anyway. I bought a set of main/rod Glyco bearings from design911 in UK (just because of faster delivery time) but I was surprised when I saw between 0.004 and 0.005 of clearance in the mains which is excessive, I tried the old ones and they went back to 0.002 consistently on all of the main bearings, I happen to have another set of Glyco main bearings on the shelf so I tried them and sure enough it gave me the same excessive clearance. also I happen to have another old used Porsche 3.2 main bearings which are almost scratch free and I tried them as well and they were all OK @ 0.002 .. Whats wrong with all the Glyco main bearings being way out of spec like that? .. I know they had a similar issue few years ago with the con rod bearings but now I see the same issue again with the mains. and BTW the con rod bearings are fine with 0.002" clearance among all 6 rods. I used both plastigauge method and mic/boregauge method just to be %100 sure. I have decided just to use the used genuine Porsche set and call it a day.

[proporsche]

was there anything wrong with the main at 180 k ?? i did mine around 300k and they were almost perfect...
Ivan

[kamaro]

Originally Posted by proporsche

was there anything wrong with the main at 180 k ?? i did mine around 300k and they were almost perfect...
Ivan

absolutely none, crank jouranls were spotless and checked %100 true. Also the old bearings were all spotless except one shell that has what looks like a small pinhole that may be caused by a trapped debris. They all were between about 0.0018 to 0.002. Except for the two garbage sets of new Glycos.

[brighton911]

Hope you saved the old ones, if it were mine I would put them back in. Sad statement on Glyco QC

[stownsen914]

With all the questions about Glyco bearings, I didn't take a chance with the rebuild I'm doing now and spent the extra for the AA Clevite rod bearings. I did use regular Glyco for the main bearings and had the machine shop measure everything.

[PeteKz]

This is one of the reasons I try to dissuade DIYers from splitting the case of a 3.0 or 3.2 engine; unless there is some other reason to split the case.

[85RedCarrera]

Here's a thread on this subject... Not all Porsche replacement engine bearings are equal:

https://forums.pelicanparts.com/911-engine-rebuilding-forum/1028696-advice-main-bearing-clearance.html

[Henry Schmidt]

Originally Posted by PeteKz

This is one of the reasons I try to dissuade DIYers from splitting the case of a 3.0 or 3.2 engine; unless there is some other reason to split the case.

These poor quality bearings are no reason to ignore a proper rebuild. Use factory GT3 main bearings and the issue of poor quality bearings becomes mute.

By not splitting the case , you have no idea what your main bearing clearance is, you run the risk of connecting rod bearing/bolt failure (number one failure that leads to catastrophic explosions in 3.0, 3.2 and 3.3 engines) and you also run the risk of a number 8 bearing o-ring leak. Over the years, I can't tell you how many engine develop a # 8 bearing leak after an engine drop. My theory is the jostling the engine around on the jack and engine stand is what often leads to an o-ring leak when no leak was previously noticed.

[mepstein]

Originally Posted by Henry Schmidt

These poor quality bearings are no reason to ignore a proper rebuild. Use factory GT3 main bearings and the issue of poor quality bearings becomes mute.

By not splitting the case , you have no idea what your main bearing clearance is, you run the risk of connecting rod bearing/bolt failure (number one failure that leads to catastrophic explosions in 3.0, 3.2 and 3.3 engines) and you also run the risk of a number 8 bearing o-ring leak. Over the years, I can't tell you how many engine develop a # 8 bearing leak after an engine drop. My theory is the jostling the engine around on the jack and engine stand is what often leads to an o-ring leak when no leak was previously noticed.

Similar to why I stated before that we rarely do top ends. Something happens during the - engine out, top end, engine reinstalled. A noise, a leak, something that was there all along but the car was trailered to the shop. Now the shop owns the problem. BTDT no thank you.

[PeteKz]

Henry, asking you if an engine needs a rebuild is like asking a barber if you need a haircut.

I'm joking. A little bit.

Remember, the qualification: "unless you have some other reason to split the case;" and this is for 3.0 and 3.2 cases only, not the magnesium pretzels. E.g., low oil pressure, case leaks, internal noises, very high mileage, etc.

Re DIYers. As a reputable engine building shop, you have to consider the possibility of come-backs and factor that into your rebuilds and costs, or refuse jobs that are too risky for you. That's why you charge $30K+ for a rebuild (and I know you put the precision and care into it to earn that money). But a DIYer doesn't have to do that.

Re bearing shells: These are not wear items in the conventional sense, because the crank floats on a wedge of oil and does not touch or "wipe" the bearings in operation (unless you run low on oil or oil pressure). If they measure within specs, and don't have visible damage, then a DIYer should reuse them. They have already proved themselves in service. Much better to do that than get a new set of bearings that are out of spec to begin with!

We've gone around on this before, and you have avoided answering directly, so let me ask again: At what point do you think the bearings should be replaced? Any time the case is split, even with zero miles? 10Kmi? 50Kmi? 100Kmi? Based on what criteria?

[mikedsilva]

Originally Posted by kamaro

I have decided to refresh my '87 Carrera 3.2 engine, just a typical rebuild, nothing fancy, and after 180,000 miles it must be due for that anyway. I bought a set of main/rod Glyco bearings from design911 in UK (just because of faster delivery time) but I was surprised when I saw between 0.004 and 0.005 of clearance in the mains which is excessive, I tried the old ones and they went back to 0.002 consistently on all of the main bearings, I happen to have another set of Glyco main bearings on the shelf so I tried them and sure enough it gave me the same excessive clearance. also I happen to have another old used Porsche 3.2 main bearings which are almost scratch free and I tried them as well and they were all OK @ 0.002 .. Whats wrong with all the Glyco main bearings being way out of spec like that? .. I know they had a similar issue few years ago with the con rod bearings but now I see the same issue again with the mains. and BTW the con rod bearings are fine with 0.002" clearance among all 6 rods. I used both plastigauge method and mic/boregauge method just to be %100 sure. I have decided just to use the used genuine Porsche set and call it a day.

um
wow.
That is a massive difference!

woud be interesting to measure the thickness of the glyco bearinngs with a quality micrometer and ball (for the concave side).
Do you have the packet they came in? Where were they manufactured and the date?

They will obviously be replaced as an extra 2 to 3 thou means they are junk!


On the topic of splitting the case; I have ONLY done a top end once since the owner had receipts for proof of a full rebuilt not that long before (in terms of miles, not time).

The engine I am working on now, is being rebuilt mainly for oil leaks and a clean bill of health. It was running and made good oil pressure...
Every rod bearing showed wear.
Every main bearing showed minor wear.

Without pulling it apart, how do you know? I would say that MORESO for diyers, they should pull it apart.. I don't know too many diyers who would want to go through the whole process again at a later stage. Most want to do it once, and once only.

[Henry Schmidt]

Originally Posted by PeteKz

Henry, asking you if an engine needs a rebuild is like asking a barber if you need a haircut.
.....edit....
We've gone around on this before, and you have avoided answering directly, so let me ask again: At what point do you think the bearings should be replaced? Any time the case is split, even with zero miles? 10Kmi? 50Kmi? 100Kmi? Based on what criteria?

You love to play this game...the "all or nothing" childish retort. I've laid it out for you before and it doesn't seem to sink in.
This 3.2 has 180000 miles on it. He's pulling apart because "he thought it was due." He doesn't have a complete history and you're telling him and anyone who will listen, not to pull it apart....why, presumable to save a few bucks.
Given the weakness in the connecting rod bolts the 3.2 design your advice is bone headed.
Your caveat is " unless there is some other reason to split the case".
There are a plethora of reasons that you refuse to admit.
First and foremost, you take them apart because over the years we have learned how to make them better.
Checking bearing clearance is one.
Replacing rod bearings and bolts is another.
Checking the oil pump for debris and wear with the understanding that oil pressure keeps these engine alive and we make the pumps work better. .
Replacing the timing chains with solid chains not master link chains.
Inspecting the timing gear for wear and backlash.
Sealing the case, especially the #8 bearing o-ring.
There is value in preventative maintenance. Period!
Peace of mind that your investment will offer continued service long after the pain of expensive parts has gone away.
You've eluded to my motives for performing a proper rebuild suggesting it's all about the fear of a "come back"
Well dude, that's pure bull-shyt and if you believe that you have no idea who I am.

[mepstein]

Originally Posted by mikedsilva

um
wow.
That is a massive difference!

woud be interesting to measure the thickness of the glyco bearinngs with a quality micrometer and ball (for the concave side).
Do you have the packet they came in? Where were they manufactured and the date?

They will obviously be replaced as an extra 2 to 3 thou means they are junk!


On the topic of splitting the case; I have ONLY done a top end once since the owner had receipts for proof of a full rebuilt not that long before (in terms of miles, not time).

The engine I am working on now, is being rebuilt mainly for oil leaks and a clean bill of health. It was running and made good oil pressure...
Every rod bearing showed wear.
Every main bearing showed minor wear.

Without pulling it apart, how do you know? I would say that MORESO for diyers, they should pull it apart.. I don't know too many diyers who would want to go through the whole process again at a later stage. Most want to do it once, and once only.

I bought a euro Carrara engine. The short block was assembled by a shop and all the other parts were included in boxes. There was paperwork describing the work the shop had completed and it all looked legit. Our policy is not to trust anything so we disassembled the engine. They used glyco rod bearings and did some other curious things. It would have been a problem if it went out with our name on it.
We had another engine come in from a well known shop. Supposedly a 3.2 short stroke. It wasn’t running right and the customer had gone to a couple shops to have it tuned. Nobody could make it run right. We disassembled the engine and noticed some problems immediately. The engine still had stock 3.0 cis p&c’s. No way it was a 3.2. What’s worse, the pistons were clocked 180 degrees out. To keep the valves from hitting the pistons, they used a buttload (technical term) of spacers. There was a ton more tomfoolery but that’s the particular thing I remember about that engine. I mentioned it to our machinist and he said he’s heard all kinds of stories about the shop. Still, the shop is championed in some circles.
These engines are pricey but it gets really expensive when you have to do something over again.

[PeteKz]

Henry, no I'm not playing a game. There's no "gotcha" here. The reason I keep asking is because what you have said before about replacing bearings does not make engineering sense to me.

Once again you have not answered a very specific question: At what point do you think the bearings should be replaced? When they exceed specifications or show damage? Any time the case is split, even if it was only run on a dyno? 10Kmi? 50Kmi? 100Kmi? Based on what criteria?

Last, I am not questioning your experience. If you say use certain sealants because they work best, and you have tested them, then I buy those sealants. If you say the best way to assemble an engine is XYZ, then I do it that way, no questions. If you say that a certain configuration of engine with a certain cam will produce X horsepower, I don't doubt that. You can't derive those lessons from engineering principles. But if you say that bearings should be replaced every time you split the case, regardless of wear, then yes, I will question why.

One other thing: You said that I advised kamaro not to split his case. Not correct. Read what I wrote. He already split his case when he started this thread. And he went to the trouble to measure his old bearing clearances, and they were within new specs. I agree with brighton911 that I would put the original bearings back in.

[Henry Schmidt]

Pete
People come here to get advice that will lead them on the best possible path to success.
Every time some want-a-be "engineer" with limited experience, recommends a half assed solution to a complicated dilemma, everyone loses. I evaluate every engine based on my experience. You can't always tell the viability of a part by measuring that part. That is why we send expensive parts like titanium rods to experts for non-destructive critical analysis. Bearings are cheap in the overall project cost of a Porsche rebuild so why risk a do over to save a few bucks. If the price is too high for you to do it right, maybe you should play in the kiddies sand-box
To answer you question again, there is no hard and fast rule but a quality new is always better than high mileage used part. "Better than new because it's tested" is what a conman says to sell his bull-shyt.

[PeteKz]

I'm trying to remain polite. Why do you have to be personally insulting and hostile in your responses?