Rod Bearing alignment of edges off

[Jonny042]

Well so much for plan C......

My AA/Clevite beraings arrived, but I didn't even bother taking them out of the package.

They too measure 17.60mm. I called the vendor (EBS) and talked with Don and he was very patient and is going to look into it, and maybe talk to AA. He asked that I send pics which I have done.

['76 911S 3.0]

This is good info, I was just about to pull the trigger on the AA bearings this week. I had the same issue with the GT3 bearings (sourced from EBS), but I threw the engine together with them anyway:

Rod Bearing Misalignment

I pulled the engine apart over the winter and am not comfortable with the offset, despite not having any issues. Patiently awaiting Don's reply and an update to this thread...

[VFR750]

Originally Posted by VFR750

This is one of GT3 rod bearings I used.

Maybe you can scale the picture to confirm the relative size of the tab on the end to see if they are now different.

I just measured the spacing of the lines on the yellow paper, they are ~9mm spacing.

My 2014 GT3 rod bearings are definitely >17mm wide and not ~17mm wide.

[Neil Harvey]

Originally Posted by Jonny042

Well so much for plan C......

My AA/Clevite beraings arrived, but I didn't even bother taking them out of the package.

They too measure 17.60mm. I called the vendor (EBS) and talked with Don and he was very patient and is going to look into it, and maybe talk to AA. He asked that I send pics which I have done.

To all with this problem.

Without promoting our business, but in order to solve your bearing issues and before you buy up every set of rod bearings in the world, consider sending us your rods along with what ever bearing set you wish to use and we look at the problem and fit the shells to your rods. We will need the rod journal sizes so we can make sure the clearances are where they need to be.

Cost, millions!

[Jonny042]

Originally Posted by VFR750

I just measured the spacing of the lines on the yellow paper, they are ~9mm spacing.

My 2014 GT3 rod bearings are definitely >17mm wide and not ~17mm wide.

Thanks for that! I'd say they match the 20mm width of the bearings that Kevin measured for us.

Still waiting to hear back. I'm wondering if maybe the answer is not simple.....

[Jonny042]

Originally Posted by Neil Harvey

To all with this problem.

Without promoting our business, but in order to solve your bearing issues and before you buy up every set of rod bearings in the world, consider sending us your rods along with what ever bearing set you wish to use and we look at the problem and fit the shells to your rods. We will need the rod journal sizes so we can make sure the clearances are where they need to be.

Cost, millions!

I appreciate the offer and no doubt that would be very helpful if needed, but it's not rocket science - putting a good stock rod, on a good stock crank, shouldn't require that sort of fooling around, especially on an engine that was made in significant numbers, as recently as 15 years ago (in the case of the GT3).

The issue at stake is not aligning the bearing in the rod. The tangs do that upon assembly, and sure, you could adjust them to center the bearing in the rod, but basically this would be a hack to fit the wrong bearing.... the issue is the bearing width is too narrow for the journal, and no amount of machining is going to fix that.

How much the missing width would affect bearing capacity, oil pressure, etc, is anyone's guess but I willing to say something's being compromised. I for one would rather have a full width bearing doing the job for me.

[75 911s]

I'm in the market for all new bearings for my long block 3.4 project so this thread certainly interests me. I see a great disparity in 3.2 main bearing pricing (200.00 vs 670.00 from Porsche dealership) So I'm guessing maybe the Porsche dealership is German made Glyco and the other is the s. african version. Well one would hope.

Thinking about the rod bearings being narrow. Perhaps there's a design change that Porsche did that proved that the rod only needed to ride on that 17mm width vs a wider (more material) bearing. It stands to reason that less material = less resistance right? I haven't seen anyone put forth a mechanical reason for the apparent change which seems to be affecting multiple vendors. Maybe there's a tech bulletin?

[Trackrash]

Originally Posted by 75 911s

I'm in the market for all new bearings for my long block 3.4 project so this thread certainly interests me. I see a great disparity in 3.2 main bearing pricing (200.00 vs 670.00 from Porsche dealership) So I'm guessing maybe the Porsche dealership is German made Glyco and the other is the s. african version. Well one would hope.

Thinking about the rod bearings being narrow. Perhaps there's a design change that Porsche did that proved that the rod only needed to ride on that 17mm width vs a wider (more material) bearing. It stands to reason that less material = less resistance right? I haven't seen anyone put forth a mechanical reason for the apparent change which seems to be affecting multiple vendors. Maybe there's a tech bulletin?

Not sure if this was mentioned, but there was a change in the rod bearings between '85-'86. According to Wayne's book, page 205.
Forgive me if this was mentioned before, but I didn't see it.

[75 911s]

That's right Gordon. It says

"Big end rod width changed on Carreras and Turbos in 1986"

[KTL]

Big end width only changed by 0.15mm at the most per the little spec book

[Trackrash]

My thought is that the .15mm may not be the only difference. Just a thought.

[KTL]

Originally Posted by Trackrash

My thought is that the .15mm may not be the only difference. Just a thought.

True. But Jonny042's bearings had been previously sized to a width that fit SC rods and those rod dimensions never changed.

[Jonny042]

Originally Posted by KTL

True. But Jonny042's bearings had been previously sized to a width that fit SC rods and those rod dimensions never changed.

Well, the plot thickens.... somewhat. I heard back from Don, he wasn't able to answer the question so he put it to Scott at AA and the answer is....... "that's normal for the application".

Now that would make sense in one way, because every single bearing I can lay my hands on (of which there have now been 4 different ones) have had the exact same width of 17.60mm. Including the 2002 date code ones that came out of my motor, which was last rebuilt in 2002.

So..... maybe that's the way it is. By all accounts Scott at AA started providing these bearings for the 911 to solve bearing failures (successfully one would hope) and making them insufficiently wide wouldn't be conducive to that.

The thing that makes no sense are the apparent existence of 911SC bearings (bearing identical part numbers, no less!!) that measure to a greater width than 17.60.

[Jonny042]

Originally Posted by 75 911s

I'm in the market for all new bearings for my long block 3.4 project so this thread certainly interests me. I see a great disparity in 3.2 main bearing pricing (200.00 vs 670.00 from Porsche dealership) So I'm guessing maybe the Porsche dealership is German made Glyco and the other is the s. african version. Well one would hope.

Thinking about the rod bearings being narrow. Perhaps there's a design change that Porsche did that proved that the rod only needed to ride on that 17mm width vs a wider (more material) bearing. It stands to reason that less material = less resistance right? I haven't seen anyone put forth a mechanical reason for the apparent change which seems to be affecting multiple vendors. Maybe there's a tech bulletin?

Mains from Porsche include the #8 bearing, so aftermarket will be aprox $420 vs $6XX.00 for factory.

Starting to believe that maybe that's just the way the rod bearings are, and nobody really notices it.

['76 911S 3.0]

Originally Posted by Jonny042

Starting to believe that maybe that's just the way the rod bearings are, and nobody really notices it.

For the record, the first time I rebuilt my engine about 5 years ago, the original 250k mile bearings that came out of the engine sit the same way. I too would feel much better about a proper full width bearing shell.

[Jonny042]

Originally Posted by '76 911S 3.0

For the record, the first time I rebuilt my engine about 5 years ago, the original 250k mile bearings that came out of the engine sit the same way. I too would feel much better about a proper full width bearing shell.

Well I'll be damned...... thanks for the data point.

I feel like the OP could chime in here soon. Maybe the 3.2 bearings have the same issu..... err.... characteristic.

[88-ben-88]

Originally Posted by Jonny042

Best course of action for you will be ACL bearings, made right there in Australia! There does not seem to be any stock in North America of those otherwise I might have used them. They are well known and a quality part - like everything else best check to make sure your clearances will be good and of course check the width!!!!

So I ordered the ACL 'race' series bearings as suggested (cant believe i didn't check their catalogue in the first place!) and was pleasantly surprised by the price AUD $150 a set (one third the price of Glyco).

However, they are the same width as the ones i pulled out, at about 17.7mm

I have not yet checked with my friendly experienced engine builder, but it seems everyone is encountering the same sized shells......has anyone located wider big end shells anywhere..???

[Jonny042]

Well it seems like they are all like that and obviously not an issue, otherwise there would be SC motors (not to mention GT3's) exploding all over the place.

I'm going to go ahead with the AA/clevite ones since they are in hand.

If I had to do it all over I'd use the GT3 Glycos I got in the first place. They were really nice, made in Germany and identical in every way to the factory ones.

However, as the GT3 bearings are not available to the OP, the clevite bearings are probably his best bet.

[Jonny042]

Originally Posted by 88-ben-88

has anyone located wider big end shells anywhere..???

Nope. Apparently they are all the same width. There seems to be some variation in the location of the notch in the rods leading to the misalignment but in the end I guess it's not that big a deal. I'm considering widening the notches to the inside by .5mm which should center the bearing in the rod and correct the misalignment.

[jjeffries]

Originally Posted by VFR750

Interesting discussion.

My 3.0SC rebuild used GT3 rod bearings and they fit perfectly. No issues with alignment or clearance. 11,000+ miles since.

2014 vintage.

Me too. 2015. We were lucky! John