While I was taking high school shop, my teacher and I rebuilt a SB 350. We took off the ridges in the cylinders, checked clearances, put the pistons in a bath to clean them, cleaned the ring lands, installed new rings, ran a glaze breaker and honer through the cylinders, etc. etc. etc.

One thing he told me NOT to do was put oil on the side of the rod bearings that would touch the rod, just the side that will interact with the crankshaft. In a newer issue of Super Chevy they say TO put oil on both sides? Is this correct?? WOuldn't this lead to a spun bearing?

Any info to help clear this up is appreciated,

Jason

 

Both


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I have never heard of putting oil between the bearing shell and the cap or rod. I don't know why they would say to do that. I know I would never do it and would slap anyone I saw trying to do it. But maybe they know something I don't, I'm always willing to learn something new.

 

Unless the bearings have a high-temp or other special coating that they wouldn't usually come with, I first take a very fine scotchbrite pad and LIGHTLY scuff the crank side of all the bearings. This removes the shipping coating they put on them. Then I clean them with break cleaner.

Definitely do not put anything on the rod or block side of main/rod brgs for assembly. They should be clean and dry. Once the bearings are installed, then I only use Bearing Guard, or some type of thick, snotty engine bearing assembly lube, with a film on both the bearing and crank.

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I'm no expert, but in all the motors I build, I make sure the back side of the bearings and the surface of the rod or block is absolutely clean, no oil or anything; I wash the bearings in lacquer thinner or other totally eveporating solvent immediately before assembly, and I DO NOT touch the front side; I oil the front, I don't find the particular lube to be very critical, I've built them with everything from STP to ATF to Mobil 1, it all works fine. I do not alter the working surface of the bearings in any way, not with steel wool, or sandpaper, or even a paper towel.

I'd say your shop teacher's instructions are closer to my technique.

If you ask any of the other guys on this site that are frequent motor builders like ede or Vader (there are plenty of others - those 2 just come immediately to mind) they each have their own personally preferred techniques too. People who are "doers" have different opinions from magazine writers.

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I have never done this before, but I would think you would want NO oil on the block (convex) side of the bearings. In theory, oil there would make them more prone to spin and ruin the block.

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like rb before i put a bearing in i clean it and the rod, cap, main, and cap with brake cleaner. i wear surgon gloves when i install bearings and use lubriplate 105 as an assembly lube, but only on the crank side. from everything i've ever heard or read you never put anything on the back side.

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As stated by the majority....no oil on the rod side of the bearing.

I've never seen anyone do that, not in any of the machine shops or general auto repair that I've worked at.

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Don't put anything on the backside of the rod bearing. Even if you did, it wouldn't spin, because there are "tabs" on the bearing that prevent it from spinning (a missing tab indicates a spun bearing when you tear one down), but there is no need to put it there, and could cause the clearance between the bearing and the journal to be to close.

BTW, I use GM's "E.O.S. Assembly lube". Its awsome stuff, but probably no better than the Permatex assembly lube I used to use before working w/ GM products.

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Ill beat it to death...
Dont use anything on the backside of the bearing, it should be clean when installed. I clean mine off with whatever mild cleaner I have and use an engine assembly lube on the wearing side of the bearing.

Why is everyone using gloves and stuff? Ive seen quite a few fingerprints on bearings

 

Thanks for the info guys. I didn't think that sounded right and as I said I was told the exact opposite by my shop teacher who claims to have rebuilt many an engine.

Thanks for the help fellas,

Jason

[This message has been edited by 89BlwnRs (edited April 07, 2001).]

 

I saw that in SC also. I can't believe they said that. What good would it do between the rod and bearing? They don't move in relation to each other. The only things lube would do on the backside is effect bearing crush which hold the bearing in place. The tabs are soley for locating the bearing shell in the rod. It would also greatly increase the chances of a spun bearing on startup.

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Why would you think you would spin a bearing if you oiled the side that's in contact with the rod? Like GMtech said your clearences would be a little tighter. But I do not think It would cause a problem. I'm sure when I rebuilt my enginne (twice, not because I oiled the outer side of the rod bearings) I used oil on both sides and It did NOT cause a problem. Oil helps controll heat right? I think it should be used on any metal to metal contact.
And I'll use it again.

Dave

[This message has been edited by 92 RSS (edited April 07, 2001).]

 

Blown,

I don't put any lubricants on the backside - only on the front side. As the rod moves around, lubrication will eventually spread to the backside as well. (I can't believe what I just read.)

ANYWAY, as for the bearing shells in the con rods and mains, you should assemble the shells clean and dry, just like your instructor instructed you.

Once the shells are seated, the locking tabs will prevent spinning. Some of the retention of the shell will be from contact with the high spots in the machined surface of the bearing bores and caps. Oil will eventially wick behind the bearing shells, but only AFTER the engine is assembled and the caps are torqued, and the oil won't make a lot of difference at that point.

As several people have mentioned, keep the bearing surfaces free from skin oils as best you can, since your bodily fluids can etch the surfaces of the bearings causing premature failure.

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Later,
Vader
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I would not use oil on the back side. But doing so would not cause the bearing to spin. Rod bearing failures are caused by insufficent oil flow. The bearing overheats and melts to an extent. This cause the bearing retainers to no longer hold the bearing and it turns in the rod. The insufficent oil flow could be to excessive clearance or truly a loss of oil to the bearing. The end result is the same. You will sometimes see a piece of bearing that has squeezed out between two rods after it has melted. It looks like a metal fillings/tailings that shows up in the scrap bin from a lathe (all curly)

[This message has been edited by jcb999 (edited April 08, 2001).]

 

Never, never allow even the smallest amount of oil on the backside of the bearing.

Oil there interfers with heat transfer and could easily cause bearing problems down the road.

In some places, oil is good; in others it ain't.

Jake

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