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Main Bearings

L

Larry Hardesty

Member
Took the crankshaft out of the Allis Chalmers C and took it to a local machine shop. The rods are 30 under but the mains are more like 32 under.

So, can I get away with 30 under bearings for the mains or will there be problems. Second question, anybody know if 40 under bearings for mains are available or not.

Paying tuition on this learning project!
 
All I see listed in the catalog I have is 10, 20 and 30 no 40. A good machine shop should be able to weld the crank up and turn it down to factory specs. Or find a used crank. I know I have one or 2 laying around
 
My e-mail is always open on Y-T. In classic you should see send e-mail in the bottom of the box next to reply. As for what the one I have look like I would have to check them out. As for a machine shop welding a crank up then turning it back down it is/was a common thing to do and I have had more then one done over the years
 
If done by someone who knows what they are doing, the welding is just fine. Lot of pullers running welded cranks and they do a lot more with them than any stock machine. Nice thing about welding is you can go back to stock. Then in 30 years when she needs re done, you only need to go to .010 under.
AaronSEIA
 
At factory spec, the bearings need about .006 shim between the halfs to get .002 clearance. If you have .002 undersize crank, you would need about .003 or 4 shim for proper clearance....... Have you tried the crank in the bearings and checked how it fits ? What are you going to do with the motor after assembly ? Daily plow puller ? Occasional use ?
 
Don't know enough to answer your other questions, but it will probably be a parade tractor. It is an Allis Chalmers C...so pretty small for heavy use anyway. All I know is that the fellow at the machine shop said the mains were closer to 32 under. So comes back to can I get away with under 30 bearings and be okay?

Thanks
 
Hay old, i have never seen it done on a crank shaft, and too old to do it now, You use the wire welder right, what wire and heat do you use? I assume you chuck it up in a lathe and slowly turn it, as you weld!!
 
IF you had shims between the cap and block then I believe the .030 under bearings could be reshimmed to work. If the block was line bored for the .030 bearings and you have NO SHIMS, then it is questionable.
 
Yup, It is a video of welding a crankshaft. another short one below. It is the way it is done to build up a journal so it can be ground back to size.
Check Here
 
I have never done the welding I let a machine shop do it. Have never been there to see it done just know it can be and has been done but again starting to be a lost art
 
The second video is of submersion welding. The arc is under the sand they feed over the weld. It's not something a guy with a stick welder does in the back yard shop. Take the crank to a good shop and ask them about doing it, or find a crank with good specs yet.
AaronSEIA
 
Asked the fellow at the machine shop I took the
crank to about welding. He does not know any one in
my town of 30,000. Nearest he knows of someone is
Denver...more than a couple hundred miles away. I
am going to try 30 under bearings. Thanks
 
I bought a different engine to get a better crank for my CA. The one that came out is .020 - .022 under on rods and mains if I remember right It could be had for not too much money :)
 
Go to pulling forum. Post about submerged arc welding. Another post about where to get one done.
 
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