[gloveside45]

I installed new main bearings 0.10 over because my crank was ground 0.10 under. I did a pre-assembly which included about 20 hand turns on the crank to check clearances, when I removed the crank to inspect I noticed a large amount of rub on the mains. Is this amount of rub normal or do I need to scrape these areas with a bearing scraper? The main were torqued to 70 foot-pounds on inside and 65 on the outside - per spec.

[TModel66]

It might be too late now but you need to plasti-gauge to check clearance. No that is not normal for a hand turn on the crank.

[Vintage 68]

No, that is not normal for a bearing to smear like that from a couple of hand turns.
Was it properly lubed before the turning?
Did you mic. crank and do a "Plasti-Gage" check for clearances?
From the looks of pictures (may just be the lighting or photo angle) the smear is only on the one side of both bearings - indicating they may not be sitting flush or the crank has a taper in the journal. Odd that it is same on both ...

I would confirm crank dimentions (journal size and taper(s) if any) and check gage the clearances before going any further.

[440sixpack]

Did you have a good lube on them and did it turn hard? hard to tell in pictures but if the rubs are smooth and you can't feel them it's probably just the surface finish which isn't a big deal. I don't care for the fact it looks to be on one side more than the other though on all of them.

I'd plasti-gage it and see where you're at, if it's tight get a new set of bearings and check it again. a poorly ground crank isn't unheard of so I'd fix the crank if needed not scrape bearings that's more for cams.

[CNC BLOCKS N/E]

It looks like there may be some tape in the housing bores or the journals of the crank. What was the clearance?? If you know.

[Vintage 68]

Originally Posted by gloveside45

... or do I need to scrape these areas with a bearing scraper?

Oh ... btw ...
I about fell over when I read this
You must be a pretty 'old's-cool' mechanic
We don't use Babbit Knives on modern insert bearings to clearance
Some of us still know how to fit poured and scraped bearings though

Can't ever throw out my trusty Babbit Knives

[gloveside45]

Yes, it is only on one side of the bearing. The reason I mentioned scraping is because the box wrench guys (boxwrench.net) recommend this if the cam bearings show high spots.

I did use green plastigage .001 to .004 on the mains, they measured .0015 to .002 - more on the .002 side. The strip was laid from front to back all the way across the bearing, no difference was noticed from end to end, it was pretty even at .002 on all mains. During the entire check i didn't rotated the crank as I didn't use lube. I did the plastigage clearance check, then removed and re-assembled the mains with clevite bearing guard and began doing the rod cap checks.

Then I did the valve clearance check, which require 2 turns per piston. That was it.

[Vintage 68]

.002" is about right, but hopefully not much under that.
If it marked the bearing, even after using a lube, then the lube isn't very good or those journals are not quite round or even across there plane ...
I usually just spary bearing with WD-40 during trial assembly to protect them and I've never had that happen - as long as the parts were machined correctly.
I would recheck that crank (or have it checked by another independant shop) before I would try another assembly of those parts.
If the crank checks out, recheck the crush on the bearing shells, they may be slightly deforming under torque and causing contact issues.
Was there any work done on the crank centerline (linebore) or the caps?

[Everett#2390]

Along with the suggestions here, mine is make sure there is no debris on the backside of the shells and nothing on the bearing saddles of the block. Clean both with Scrotchbrite and wipe clean with WD40.

Might check the bearing thickness in different places ensuring the shells are the same thickness throughout. Use a known section of round stock for the crankshaft journal side and subtract the round stock diameter from the overall thickness measured.

[440sixpack]

.002 is pretty standard so if you're that I wouldn't worry. if you turned it that much without lube I'd expect the bearing to rub the surface finish off, lube it up and go. it's always a good idea to lube and spin eveything as you assemble the block, the crank and more importantly the cam. if you can't turn it easy you have a problem and you can address it then.


Scraping cam bearings is real common, 90% of the Mopar and AMC's I've done require it . I'm told they're worse but I can't imagine GM is immune .

[gloveside45]

The only time I turned the crank was when a nice even coating of Clevite Bearing Guard or a small dab of oil was applied, at no other time when the bearings were dry did I rotate the crank. The platigage clearance check on the mains did not require me to lube them, only put a dab of oil on the lower bearing for the 1/4 rotation needed to install the 3rd and 4th cap for their clearance check. Once the clearance check was done I removed the caps, cleaned the plastigage and then removed the crank and fully lubed the bearings for the journal clearance checks.

I used dry paper towel to clean all surfaces before installing the bearings. I used laquer thinner on the block to clean those surfaces as well.

Everything rotated smoothly, no binding or anything once all the pistons (without rings) were installed and the valve clearance check was done. Everything seemed to move great, so I'm hoping this isn't anything major.

[gloveside45]

Here are some much better photos of the bearings....

[Vegas69]

I'd put a mic on that crank.

[gloveside45]

Originally Posted by Vegas69

I'd put a mic on that crank.

The crank was ground and mic'd by the machine shop, you think they messed up?

[Vegas69]

Seems strange they are all wearing on the same side of the mains. I'd take it somewhere else and have it mic'd before I went any further.