Steel Main bearings

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Glen Getchell
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Steel Main bearings

#1 Post by Glen Getchell »

I'm sorry for making this a new topic, as I know it has been discussed. But these computer thingy's confuse me, and I could not figure out how to get back into a thread from years ago. And if I did, if it would post as new.

Anyway, the last posts I could find regarding this subject seem to be around 2014. Has there been any change in opinion on the use of steel backed main bearings? The cost, and the cost difference is just plain staggering. Checking the price of steel backed bearings just had me say out loud. "It figures." After seeing the price of the alloy bearings, I believe I may have fainted and hit my head because I have a headache, and the only thing I can remember is $726. They are twice the price!

So far what I have read seems to be 50/50 for and against with both sides represented by highly respected experts. Has any opinions changed (or have the bearings changed) since this was last discussed. We are talking a huge difference of price on something that is already over priced. Thanks

Glen
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David Jones
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Re: Steel Main bearings

#2 Post by David Jones »

Glen, I recently talked to a few friends about this very aspect as I am in process of building two engines. A general opinion appears to be that the steel backed bearings are good for street use but start to push the envelope and you better have the alloy bearings. On the two engines I am building the split mains were steel backed and they were Porsche original bearings according to the logo inscribed upon them. As I have not yet bought my bearings perhaps someone can say if all the bearings are now steel backed including #1 and #4.
If I had known I would live this long I would have pushed the envelope a little harder.
Cymru am byth
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Brad Ripley
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Re: Steel Main bearings

#3 Post by Brad Ripley »

New Kid in Town -- actually been around for a few years -- see https://aapistons.com/collections/engin ... erformance Their bearings are alum alloy and come in early and late cranks, std thru 2nd on the case/std thru 2nd on the crank. About $250/set.

Steel-backed version from Germany sell at $400 to $545 depending on outer/inner sizing.

Old original aluminum ones can only be found on Ebay, etc.

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Glen Getchell
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Re: Steel Main bearings

#4 Post by Glen Getchell »

Has anybody had an experience with these AA bearings? I did not have good luck with a AA P/C set. Rings failed after 20K miles on a street car.

At a risk of sounding like an idiot, my interpretation of steel backed bearings is not what I thought. I thought all four bearings were steel backed not just the center two half bearings. Now that I know this is not the case, I can say that I have never actually even seen an all alloy bearing on any engine I have pulled apart. I have two apart right now and both apparently have steel back bearings in them. Both engine had upper end failures (related to rings and pistons) (not including the one mentioned above which also had a ring failure). So apparently I have been competing with steel back bearings for the last 10+ years (the last time the one engine was opened up).

But with that said, the price of the AA bearings is intriguing for all alloy bearings. But despite my shock at the all alloy price from one of our biggest vendors, I am looking for the best option with price considered, but not the only consideration. So I wonder if the AA Alloy are better than the German steel backed versions?

Glen
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Martin Benade
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Re: Steel Main bearings

#5 Post by Martin Benade »

CJ should have some input here. CJ, are you missing? We have not heard from you lately, but pretty sure you have remained out of jail.
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Jacques Lefriant
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Re: Steel Main bearings

#6 Post by Jacques Lefriant »

Hi Glen
the all alloy bearings are the early bearings for the 50mm crank. C/SC/912 have always had thin wall steel backed #2+3. The issue now is that the latest bearings from Germany? come with steel #1+4. i have made previous postings that suggest that if i were doing them i would have increased the crush or the O.D. of the bearing to maintain some crush. Machine shops such as CE and Ollies take this into account in making their recommendations as far as sizing the case. The bearings from AA are a seasoned product but the responsibility for checking dimensions rest with the engine builder. one thing to check for is the proper radius to match the crank since you can get a false end play and eventually end up with fracturing the flange.
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Vic Skirmants
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Re: Steel Main bearings

#7 Post by Vic Skirmants »

I have to add some input here. For years, I have bad-mouthed the steel #1 main bearing; probably not enough crush, wrong expansion rate, whatever. I may have to re-think all of that.
Last Friday at Waterford Hills, first lap of practice, fourth corner, the fresh engine seized suddenly enough to lock up the rear wheels and throw me off the track; luckily into a grassy field, not the forest on the left. In 54 years of racing, I have had various engine failures, none of which locked the engine completely. Yesterday I tore it down and the #1 main bearing seized. Heat and a press failed to move it at all. I will have to split the bearing to get it off. The locating dowel pin was sheared off flush.
The bearing was a factory aluminum bearing, .25mm OS, machined by JL to the standard dimension; yes, I checked.
JL, what do you think?

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Jacques Lefriant
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Re: Steel Main bearings

#8 Post by Jacques Lefriant »

I am sure you checked but the Scat cranks have a big radius so some bearings have to be modified to accommodate. That said another engine builder i know has had #1 problems but the failure mode was the flange breaking off and the bearing fractured. in a stock engine this should not be a problem since no elevated temperatures and lots of oil flow. the difference in the failures you and the other builder experience is probably due to the difference in the alloys. the genuine ones differed in alloy but were cast and soft. the AA style are wrought and harder. There are probably too many variables to establish a primary cause so i think the other builder has concluded he will use the steel #1 for his engines and have the machine shop dictate the measurements. Another builder will use AA bearings but coat them. That said i have not heard of any similar failures from the DIYs and regular shops that have used the AA style alloy bearings.
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Michael Foster
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Re: Steel Main bearings

#9 Post by Michael Foster »

"Another builder will use AA bearings but coat them". Can you explain this Jacque?

Michael Foster
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Jacques Lefriant
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Re: Steel Main bearings

#10 Post by Jacques Lefriant »

Hi Michael
coated bearings are done by many vendors http://www.calicocoatings.com/bearings/ the alloy bearings usually have a flash plating of tin in the old days lead was used now it is verboten. if you go to file:///C:/Users/Dell%20User/AppData/Local/Microsoft/Windows/INetCache/IE/A5AWOC6C/clevite-77-rod-main-bearings.pdf you can see the thin wall bearing options and still coating is considered. I don't know what the steel bearings are equivalent to as far as construction but they do appear to be tri-metal. Silver was considered to be the ultimate surface to use back in WWII for bearing serviceability. for what we pay forthese bearings they could be Gold plated at least.
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Martin Benade
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Re: Steel Main bearings

#11 Post by Martin Benade »

Is the coating done for wear reasons, or to increase the crush? Is it only on the inside wear surface? I would think that bearings are already pretty carefully engineered with compatible layers. Is it really advisable to add anything?
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Jacques Lefriant
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Re: Steel Main bearings

#12 Post by Jacques Lefriant »

Hi Martin
when the oil film is present the surface is of little consequence. dry start ups, oil starvation or not enough pressure etc you want something better.
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