Loose main bearing outer race

Hello,
I know this topic has been covered, and I have read through lots of posts. I just installed new superblend roller bearings, listed as SKF on the website but the boxes say Baker bearings. Everything seemed fine on the installation in the heated cases, however when I was turning the case over in doing something else, the drive side bearing had partially fallen out. I took it the rest of the way out and found that it is almost a drop in fit with the case cold. The timing side seems tighter, but I am sure will still spin substantially with the engine warm.
Just out of curiosity, I tried the old german FAG bearings, and there would be no way to put them into the bores without heating the cases up substantially. When I measured the difference between the original bearings and the new ones' outside diameter, there is a difference of 0.004".
It sounds like loctite doesn't work, I saw the set screw and washer drilled halfway in the bearing and halfway in the case, but that sounds like machine shop work, in which case I may as well have them do it right and weld and rebore. My concern is why the outer diameter of these new bearings is so much smaller, and I don't want to pay a ton of money to have them machine the case to a smaller diameter than what it should have been.
I would appreciate any suggestions, because right now I am getting ready to put the original bearings back in and pretend like nothing happened.

I'd return them and try a different supplier before I'd mess with trying to install them. You have a good case for a refund if there is .004 difference. If they give you any crap, let us know who they are and we'll see they get outed on here. Shoddy supplier.

I will contact them. Problem is I already had installed the inner races prior to this, and for me to get the old ones off it took me cutting a groove in the back of it to get the puller behind it, not sure if these would come off any easier.

Are you using a bearing splitter?

Yes, but it doesn't get behind it enough, it just grabs the side of the collar

You can borrow one at Autozone. Maybe a different one would work better.

Did you buy these from a bearing supplier or a Norton parts supplier?

The inners have to come off and the bearings sent back.

You need this type of bearing puller for the inners. Grind a sharper edge on the seperators if needed.

Did you MEASURE both bearings?
Doing this type of engine repair, you need access to precision measuring tools. If not for the visual cue, you'd have had a ticking time bomb.

Correct me if I am wrong, but you chose to buy from a cheaper supplier and the part you got isn't the part you need, right? Or even the part you thought you ordered.

Unfortunately when this happens to me, I have normally ended up swallowing the cost of the cheaper part and paying for the part I needed!

So I really try to choose the right part when it is critical. Main bearings are 'somewhat critical', refer to concours' response.

Bite the bullet and buy main bearings from AN or another reputable source of the same bearing, and I really mean the same bearing.

No bearing should be 4 thou out on OD, or any other dimension. The internal clearance tolerance is in microns as an example, 4 thou on that is worn out before even fitting.

When you look after baker bearing , you could see it's only a bearing supplier , not a manufacturer , so may be the box is baker printed , tho you should find the manufacturer brand engraved on the bearing outer , and what is the name ??

I believe that dimensional tolerance for that class of bearing is +0/-.0005 inch.

Lots to reply to.
Kommando, yes, that’s exactly the setup I have. I will try grinding the splitter down as it isn’t a very sharp edge.
I didn’t think I was ordering the cheap crap, they are 100 usd apiece and from a Norton parts supplier and were the only option I saw. I don’t want to say where until I have talked to them as you guys seem fired up and I doubt they are intending to sell junk.
I measured the OD with a digital micrometer. That on the other hand is not high quality, but I have used it for lots of engine work and it seems to work fine.
That makes sense for the packaging if baker is a distributor.
In any event, this does not sound right, and it sounds like you all feel like I have the wrong bearing and not a worn out case, which is great news. I would much rather eat the cost of the bearings.

And just looked again. The bearing is marked MRC R306 G 3

Also while I am at it with my obvious inexperience, my end play was 0.018” prior to tear down, 0.016” with the new bearings and no case sealant. I have 2 0.003” shims, the kind that go behind inner race. Since I have to pull them off anyway, would you install them or leave well enough alone? And if install, one on each side or install connecting rods and barrels to see which side would give me the best centering?

Aiden said:

Also while I am at it with my obvious inexperience, my end play was 0.018” prior to tear down, 0.016” with the new bearings and no case sealant. I have 2 0.003” shims, the kind that go behind inner race. Since I have to pull them off anyway, would you install them or leave well enough alone? And if install, one on each side or install connecting rods and barrels to see which side would give me the best centering?

Click to expand...

I do not bother about endfloat below 25 thou, its a whippy crank so needs some space to do its thing. The exception was a 72 where there was evidence a crank cheek was kissing the inside of the driveside case so I put a 10 thou shim on that side.

Aiden, aside from the size issue, I believe you need a bearing with an E suffix.
The E gives you "Optimized internal design for increased load carrying capacity". Norton gave this type of bearing the name " Superblend"
It's a higher quality bearing than the same size mainbearings Norton used prior to the Superblends.

Glen

MRC are part of SKF

The historical perspective of MRC MRC is the outgrowth of three of America’s oldest bearing companies—Standard Roller Bearing Company, Gurney Ball Bearing Company, and Strom Bearing Company. In 1986, the Bearing Division was acquired by the SKF Group, which is an international manufacturing and marketing organization composing approximately 200 companies with 85 factories, together operating in more than 130 countries. SKF sales units are backed up by nearly 200 sales offices and over 10,000 distributors and retailers.

Somewhere in here


Is what the G means, could be the MRC version of E but at 396 pages it a tough task

Thanks kommando and glen.
Will leave the end float alone. Whatever the terminology, it is clear these bearings won’t work.
I have contacted the supplier to see if returning them is possible.
How do you feel about this option:
They offer both CN and C3, but it sounds like C3 is generally recommended?