I have a set of NOS Main bearings and the coating on one of the split bearings is de-laminated. These have never been in an engine. Anyone seen this before? The other bearings all look OK. They are part number, 539.174.85 (1st OS x 3rd US). I looked in my bearing stash and noticed that all of my NOS Porsche-labeled bearing sets were coated as shown below and all of my NOS Glyco bearing sets were not.
I've never thought about doing this on a 356 engine before, but because these are somewhat rare I may try coating them. Has anyone had success with bearing coatings on a 356/912 such as http://calicocoatings.com/ or someone else?
FWIW: I define NOS as something made prior to about 1970. These sets are probably over 40 years old.
Some 911 engine builders polish the inside of the bearing with fine scotchbrite and then coat them with Dow Corning 321 dry film lube. You might want to do a search (Dow 321) on the Pelican engine build forum.
Never read anything about Porsche 6-cylinders, but this was a 'hot tip' for SBC hot-rodders about the time forged pistons needed .008" cold skirt clearance.
To paraphrase Mark Donohue, 'They were noisy, but they didn't last too long'.
Ken,
Thanks, I found this thread http://forums.pelicanparts.com/911-engi ... ality.html about newer Glyco bearings of poor quality due to high spots from the coating. Interestingly, a professional 911 engine builder said that he sands the bearing with 600 grit wet/dry and then sprays it with Dow 321; but I would would prefer to use a coating that bonds to the surface and I'm not sure if Dow 321 is any more than a lubricant. I found that NASA tested it http://ntrs.nasa.gov/archive/nasa/casi. ... 004345.pdf and it appears to be a good long term assembly lubricant for engines that might sit a while. I might try it for that purpose.
Thanks
Vic! Cliff! Ron!
Stay focused guys.
Have any of you seen old bearing coatings do this? I assume it was an early moly-type coating and I'm looking for a way to salvage these bearings. Still seeking ideas.
Thanks
John
John,
Sorry for the allegory, but my point is simply:
If the bearings aren't right coming from the supplier, send them back. If they aren't right and you can't send them back because they're too old, throw them in the trash.
Plain-bearing tech is complex, and I have no knowledge that would suggest other alternatives; it's beyond my expertise. If you get *reliable* advice from others, I have no problem with that. Take that advice and do what you please.
(BTW, that corrosion evident in the oil hole suggests to me that they've been living in a moist environment for too long. To me).
Hi John
A good plan would be to send them to a vendor like Calico. They have experience with dare i say it VW bearings etc. They probably will lightly abraisve blast the old coating off and apply a thin coating of a proprietory coating and then bake it. they will then tell you to burnish the coating with scotchbrite or some other method. Fear not the top VW engine builders swear by this process. The cost is minimal about $10 a journal. I would not attemp the DIY solutions or trust a not recognized vendor.
KTF
jacques
I'm remembering some tech bulletin from General Motors, I think specifically Oldsmobile.
They warned against using scotchbrite because of the possibility of contamination from the abrasive. They had traced several engine failures to the use of that product. That's all I can tell you.
Jacques, what are they trying to accomplish? What is the technical advantage? Why do they suggest that YOU Scotchbrite instead of THEM doing it in a controlled and expert way? I would also think that the chance of leaving dirt behind after Scotchbrite is dragged across your bearing is very high. How does this jive with F1 practice of assembling engines in chambers that are 99.9999999% dust free? I am sure they know what they are doing but I don't think I could go that route unless they were the only set of bearings in existence.
'57 Speedster
'59 Sunroof
'60 Devin D Porsche Race Car
'63 Cabriolet "Norm"
'67 911 S Original Owner
'03 Ferrari 575M
'09 Smart Passion
Vic , Ron, Cliff, That thread on Pelican was 4 years old I thought it was scotchbrite but I guess my memory failed me it was 600 wet or dry sand paper.
Ken Gregory wrote:Vic , Ron, Cliff, That thread on Pelican was 4 years old I thought it was scotchbrite but I guess my memory failed me it was 600 wet or dry sand paper.
Even worse! dirt dirt dirt
'57 Speedster
'59 Sunroof
'60 Devin D Porsche Race Car
'63 Cabriolet "Norm"
'67 911 S Original Owner
'03 Ferrari 575M
'09 Smart Passion
bearings are soft so that contamination can sink into them and not score the crank. If you build the engine carefully and keep the the oil clean it will be a very long time before dirt causes problems. When you sand your bearings you will fill them with dirt. What sense does that make?
'57 Speedster
'59 Sunroof
'60 Devin D Porsche Race Car
'63 Cabriolet "Norm"
'67 911 S Original Owner
'03 Ferrari 575M
'09 Smart Passion
I have a friend who"s built multiple winning Baja 1000 race motors who scotchbrites his bearings. The shop he worked at won Score engine builders of the year more than once. Don't fear the scotchbrite! (unless your building yours to send to the moon.)
Scotchbrite off the crap and dial bore them in the case. If it was a VW bearing, I'd throw it away and buy a new set for $35.00. Why are there so many glitter parts reproduced, but when it comes to consumables like bearings, were lucky to find the right size and happy to pay WAY, WAY too much?
