Farm Equipment - B bearings opinions wanted

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B bearings opinions wanted

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=7984
Printed Date: 30 Jan 2025 at 11:43pm
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Topic: B bearings opinions wanted

Posted By: Denis in MI
Subject: B bearings opinions wanted
Date Posted: 11 Feb 2010 at 9:14pm

On my 1938 B I am trying to reassemble my journals on the spare crnak I had measure out

Front Main: 2.248

Center: 2.248

Rear:2.248

Rod 1: 1.934
Rod 2: 1.935

Rod 3: 1.935

Rod 4: 1.935

Shop manual says Mains: 2.2495 and rods: 1.937

My question is will standard bearings give me the correct clearance or do I need .002 undersized are bearings made so that once shims are installed they have the correct clearence and crush with the size of my journals will .002 undersize give proper clearence with shims installed and if I they don't what would happen if you removed all shims to get proper clearance

Thanks in advance for all help and opinions,

Denis

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1938 B, 1945 B, 1941 IB, 1949 C, 2 1938 WCs, 3 1950 WDs, 1951 WD, 2 1955 WD45, 1957 D-14

Replies:

Posted By: Gerald J.
Date Posted: 12 Feb 2010 at 9:43am

First you have to find out if the main and rod journals are round. Rod journals tend to wear more on the side with the power thrust. Most wear is just after top dead center on the power stroke. Then you need to keep the couple thousandths working clearance from the largest diameter and decide if more clearance is going to cause too much loss of oil pressure.

But .002 under bearing inserts are made for the case where the crank shaft is worn, but not too out of round. Its much cheaper and quicker to use those inserts than to grind the crankshaft. But then you can get that by removing shims though somewhere in that process the hole in the inserts isnot round either.

Gerald J.

Posted By: Denis in MI
Date Posted: 12 Feb 2010 at 10:12am

They are round and no taper either, the big thing I guess is if the bearings are made to have correct clearance with shims installed or if shims will increase clearance at which point I would need .002 bearings, I am fairly sure I will need the undersize on the rods anyway

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1938 B, 1945 B, 1941 IB, 1949 C, 2 1938 WCs, 3 1950 WDs, 1951 WD, 2 1955 WD45, 1957 D-14

Posted By: Ken in Texas
Date Posted: 12 Feb 2010 at 10:32am

Good luck finding .002 bearings. A new shim stack is .010. 4 to a stack. Plastigauge and remove .0025 shims as needed using standard bearings.

Posted By: Dick L
Date Posted: 12 Feb 2010 at 12:17pm

With this type of oiling systen you need not be concerened with the side clearance as long as you are not out of round on the journal.

I will place the link to pictures I took of the bearing filing which is what will be needed in your case. The .002 clearance would be measured with the pistons at bottom center.

You measure the journal and then clamp the new berings into two rod caps and measure that diameter. You will want the inside bearing insert diameter to be .004 larger than the rod journal. That will give you .002 crush and the .002 clearance when properly shimed.

After filing the bearing inserts you will want to mark which journal you have fit the bearing to. They all look alike when you are done measuring and filing and you probly won't want to measure all over again.

Not filing th einserts will crush th ebearing inserts enough to crush the inserts at the parting line and pus th ebearing in towards the rod journal and lock the crankshaft from turning.

http://public.fotki.com/DickL/allis_chalmers_engi/filing-main-and-rod/ - http://public.fotki.com/DickL/allis_chalmers_engi/filing-main-and-rod/

The pictures are not in order so you will have to fish around to see what I was doing.

Posted By: Ken in Texas
Date Posted: 12 Feb 2010 at 1:20pm

Denis. Listen carefully to Mr Dick L. He has it all together when it comes to B/C&CA engines. When he quits posting replys it will be a great loss to the forum and the hobby.