Possible main bearing issue

[brighton911]

Hi everyone and Happy New Year. Like a some others with winter engine rebuild projects, I need a bit of guidance. I am now down the cases on my 3.2. I have checked the main bearing clearances with Plastiqauge and they all came out to .002", within spec. The surfaces are really good so I am inclined to re use them but, as you can see from the pictures, there is what I call staining where the bearing sits in the crankcase and the back side of the bearing. This issue is only on number 2 and 6 bearings. Is this staining an issue? There are no shiny spots to indicate the bearing is moving in the case and they all fit snugly. Comments welcomed and thanks to Pelican for hosting for the greatest resource a guy could ask for. The collective wisdom of the forum would be difficult to measure.

[Walt Fricke]

I've got a bag full of bearings which looked like I could reuse them. Never dared, though.

I've often seen the information stamped into the backside of the bearing transfer to the bearing saddle. I'd think that if you can't feel anything where there is discoloration, that's not an issue.

[Jcslocum]

This looks like metal fretting to me and you should do some reading on the subject. I'm not an expert at this but know it when I see it. I also have no idea if the fretting you have would make the parts NFG or not. Experts here will know.

[Gordo2]

Don't know what it's from or if it's anything you should be concerned about.

I'm pretty sure my bearing saddles had a bit of similar discoloration. Unfortunately, it doesn't look like I took any pictures prior to cleaning the cases.

I do know however, that I cleaned the bearing saddles with some carb cleaner & Kimwipes when I was cleaning the case halves. This was after pressure spraying and stuff - no stains prior to reassembly:



Have you tried cleaning them up? I would think if you can remove the discoloration with some alcohol/carb cleaner and the surfaces appear good - then you are good to go.

As for re-using the bearings - that's a judgment call you will have to make. I re-used mine primarily due to the apparent poor quality control people have reported on new bearings, and the fact that the bearing had less than 30k miles, looked good and came up with good clearances.

Good luck,

Gordo

[keynsham1]

Your marks are on a non moving interface. It could be a number of things but it will not effect the operation of the bearing. If the bearing faces are clean, undamaged, and still a light grey colour, then it is fine to reuse them. This forum is full of advice which is only opinion of individuals, and in my own experience is regularly misguided. Tread very carefully, or ask an independent professional if you want a definitive answer, don't trust any internet forum.

[brighton911]

I checked with a number of area engine rebuilders and they all said it was no worry. One tech asked if the bearings came from a running engine as the working surface on all are almost as good as the day they went in. Like Gordo, I am concerned with the reports of so-so guality on replacements (Gylco) so the originals are good for me. Thanks to all for the input,

[BURN-BROS]

I have come across an engine that have a crank bearing bore out of spec. The result was the bearing moved around in the case a bit, nothing too horrible. The engine had 300,000 miles on it and the issue could very well have been from the factory.
If you have a out of spec crank bearing bore, then having a machine shop take a couple of thousandths off the case halves and line boring back to standard is the route I would go.
If you do not want to go that route then you can try bearing loctite....but I would not know what the success rate is.

[dmark9]

I had a little of that on my 964 motor too. I cleaned it and installed the new bearings and all is good on my daily driver.

dmark9
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