Bearing Wear Question

[Rich76_911s]

Hey Guys,

I'm in the process of rebuilding my 1987 930 engine. Tear down has gone really well, with only one broken head stud. You can follow along here: Engine Rebuild Rich76-Style

That said I have what seems to be strange bearing wear.

The front of the bearings look fantastic.



The back of the bearings however have some pretty significant wear, as seen here:






These appear to be the original bearings with date codes of 06-86, and the car has done about 95,000 miles. Is this normal wear or is it something I should be concerned about?

Thanks
Rich

[afterburn 549]

It is "shuffling" in the case , That is I am guessing it is lose.
Is it the correct size?
Was it line bored ?
Does it fit into the saddle snug?
I have rcvd bearings packaged wrong.......

[Rich76_911s]

Hey Afterburn -

Thanks for the response and questions!

These are the original Bearings that Porsche put in the engine. I just split the case for the first time. So I doubt the engine was line bored.

THey did fit in the saddle pretty snug. Certainly didn't feel loose or fall out without assistance.

Rich

[afterburn 549]

Thoroughly check line bore, and bearing size- and undersized, as that wear shows looseness within (shuffle)
Aluminum cases AFAIK know do not have this problem of line bore......but obviously, something is wrong there.
Being a turbo........
Maybe lugging the engine?

[KTL]

Do you know for certain if the engine case has ever been apart before? Reason I ask is because someone could have split the case before and reused the bearings. A trick some use is to sand the plating off the back of the bearings to give them more "bite" in the saddle.

Nothing wrong with reusing bearings if they all look good. Especially since the quality of new bearings these days leaves a lot to be desired.

[afterburn 549]

It looks very "shuffled " to me. Look at the layers worn off as the wear goes dwn through.
i am not saying i am right by any means, but is my best guess .

[Rich76_911s]

I suppose it is possible the bearings were taken out and reused. I don't know how'd I'd be certain it hasn't ever been apart before.

I was planning on using GT3 bearings, not reusing these.

[Steve@Rennsport]

Stock boost pressure?

[Rich76_911s]

Hey Steve,

Yes stock boost pressure and just a 3ldz. Car was basically stock except it had Fabspeed exhaust on it. Actually since I've owned it I don't think it ever had over .7 bar, and there was no adjustable boost on the car.

-rich

[Mark Henry]

Lets see the bearing saddles in the case.

[Steve@Rennsport]

Rich,

Two things;

1) Are those bearings factory, aftermarket Glyco, or something else?

2) Picture of the case saddles?

Generally speaking, shuffling is caused by excessive boost, detonation, and/or poor fitment. The working surface of the pictured bearings looks like new, however the backsides display some shuffling.

Date codes are not a positive indication of originality, only date of manufacture and sometimes these can be in an inventory for some time.

[Rich76_911s]

Thank you all for your continued help in diagnosing this issue.

You can also see on the large bearing before the flywheel there is some where on the inside edge of the bearing:



Here are some photos of the saddles. There are no grooves or roughness to the saddles more appears to be stains than actual wear on the saddle surface.

[afterburn 549]

Thats your crank thrust bearing and pretty normal.
Everytime you step on the clutch you are pushing the crank , thats the wear bearing for it
or Thrust bearing .
I would say at the least, have an experienced person take a NEW main bearing and push it into place .
It should go in nice and snug, maybe nice and tight is the word.
If it falls in there or is a light fit you have line bore issues for sure.
Again I am not the last word on this.
Of course you can send it to the proper shop and have them measure it all up for ya.
Which ever makes you sleep better.

[Mark Henry]

It is bearing shuffle, I've seen this three times and every time it was a turbo engine.

First torque the empty case, take it to a machinist and have them inspect the saddle bores with a bore gauge. Wayne's book has the specs.
If it's within spec and you are still worried about shuffle, you could glue the bearings in place with Loctite 620 sleeve fit.

[Rich76_911s]

Thanks Mark and Afterburn!

I am going to take the case to the machinist and have them inspect the line bore. The jerks I'm dealing with had the NERVE to take this week off, so I'm stuck waiting But the car is loaded up with everything and I'll be going by next week. I'll keep you abreast of the results.

What would be the cause of the shuffling?

Someone on the turbo forum suggested it might be lugging the engine. I did have an overly rich midrange that was resulting in lugging conditions. For example if you were cruising on the highway in 4th and wanted to pass someone, you'd give it gas, turbo would begin to spool, AFR's would drop below 10, black smoke, and no boost build up with no acceleration. It did the same when you went to climb a hill. It did this the entire time I owned the car, and who knows how long before I owned it. I fixed the issue with an adjustable wur.


Cheers
Rich

[Mark Henry]

To me 'lugging' the engine is driving below 3000rpm
This is bad for an aircooled engine because the fan needs to be up to speed to push enough CFM of air. Accelerating at 2000rpm creates a huge amount of heat that can not be cooled, uphill lugging and cylinder head temps go through the roof. Heat cycling the engine like this causes head damage, increased wear from heat cycling and the breakdown of oil.
In traffic when rpms drop to 3K you really should be gearing down to accelerate.
Not sure if this would cause the bearing shuffle.


Now if the turbo is hammering the boost on at a certain level then that could be the source of the bearing shuffle.

[afterburn 549]

Here is a REAL word of advice, dont just let "any" shop work on the case.
Pick someone that has done a few.

[Rich76_911s]

Thanks Afterburn. Going to Verden Tool in New Jersey. A pretty well respected Porsche Machine shop with a lot of experience.

Mark I'm guessing that 3LDZ wasn't "hammering" anything too hard.