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Join Date: Jul 2013
Location: Brisbane, Australia.
Posts: 681
964 Main Bearing Thickness - Clearance

I have pulled my 964 motor down to fix some oil leaks between cylinders and the case.. so, now I have the case apart and thought it prudent to replace the bearings.
My current bearings are original and have travelled approx 65k miles. They are in very good condition, but seeing as a new set of Glyco from Pelican Parts are only a few hundred, it seems silly not to change.

Well, I did a dry run, and used plastigauge to check my clearance. To my surprise, my clearance came back at 3 thou of an inch; this seemed a bit more that I would have thought.

So I pulled the case apart again, re-installed my old bearings, and ended up with 2 thou.

Can it be that my NEW bearings are thinner than my old bearings?

Using my digital micrometer with a ball bearing on the anvil, I checked some of the bearings and on average, my new bearings measure at 2.49mm and my OLD bearings measure at 2.50mm... 0.01 of a mm difference.

I am borrowing a bore gauge from work, to try and be more accurate, but what would you do in this position?
I am contemplating using the old bearings... at least I get the thou back. The car is just a weekend driver.

Last edited by mikedsilva; 08-07-2016 at 09:44 PM..
Old 08-07-2016, 09:41 PM
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Location: Ayrshire, Scotland
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Hi Mike,
See this thread
Rod Bearing Controversy

Where were your bearings manufactured, Germany or South Africa? Should say on the box. There's been some major issues with the ones made in Africa, these are much cheaper than the ones supplies by Porsche which are checked to be within spec but obviously cost a hell of a lot more.
Old 08-08-2016, 02:29 AM
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Well, mine are made in Poland...
From the reading I did, it seemed that it was only the rod bearings that were suspect.. I ended up buying those from Porsche.. you can see the sets of marks where they have been measured.

But I didn't see much negative publicity on the main bearings, hence I just bought from Pelican.

Not sure if I should be asking to return them and even if I did what other options are there?

Plastigauge shows that I have a clearance of 3 thou.... I'm still trying to find out what an acceptable clearance is....

Perhaps I should just run them?
Old 08-08-2016, 04:46 AM
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Old 08-08-2016, 05:30 AM
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Hi Mike,
Firstly I'd advise you to get a reliable micrometer to measure the bearings, it's reasonable to presume that a new bearing would be a tighter fit than an old bearing.
Also from the picture you posted, it looks as though the plastiguage has only crushed on half of its full length, I would have thought that the gauge should have crushed evenly throughout the full width of the bearing.
I've never used this plastiguage to measure clearance before so hopefully someone with experience of using this will come along and give their thoughts but to me it looks as though roughly 50% of the gauge hasn't been crushed which would give a very excessive clearance at the uncrushed part (I'm going by the first pic you posted)
Good luck but don't build it back up until you're sure things are ok.
Old 08-08-2016, 11:24 AM
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Thanks... I have ordered a micrometer set...
Also, after a bit of searching and contacting respected builders in the USA, it seems that no one recommends the Glyco bearings, whether they are for mains or rods.

I have a set of "genuine" rod bearings already and have ordered a set of "genuine" mains too. Why the ""?
Because as we all know, the Porsche bearings are made by Glyco, but measured and accepted by Porsche...
What annoys me, is how can Glyco get away with selling them if they are susceptible consistency? And if it is fairly common knowledge, how can Pelican continue to distribute? I can only summise, that some people buy the cheap ones for "cheap rebuilds".. ie, a nice clean bearing with slightly imperfect clearance is better than a screwed up bearing.

As you can see from my post count, I am only an amateur so nothing I say should be taken as fact.
Old 08-11-2016, 03:43 PM
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Yeh it's hard to believe that the same company who make the manufactures bearings can turn out something which is sub standard and completely out of spec but hey ho it's cost you a wad of cash but at least you'll know that when you button up your case you'll not have to look at it again , for the peace of mind it's worth the expense.
Hopefully you'll get your money back for the first set you bought, and yes you should bring this to pelican's attention, in my opinion they should stop stocking these bearings until glyco resolve the issue, good luck with the rebuild, also take credit where credits due, you maybe an amateur but you diagnosed an out of spec part, if you continue to check and double check at each stage there's no reason why your engine won't run like it's been built by a pro!
Logan
Old 08-12-2016, 12:47 PM
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