Allis B engine rebuild

I have half a dozen B tractors.  Most have "overhauled motors". I have never had a crank turned, or  block line bored.  My "standard overhaul" is complete disassembly, mike everything, see if I can reuse the bearings with new shimming,, or buy new bearings... I hone the cylinders, new rings, lap the valves... a new guide now and then ... and all new gaskets. I have pushed the limit on cylinder taper and journal "round ness" a few times. You just have to know exactly what your doing, as Dick said.. With a carb overhaul and a good starter and mag, they roll off on 1-2 revolutions of the motor and run great.

Edited by steve(ill) - 03 Sep 2019 at 8:54pm

When I get done rebuilding an engine with shims I feel I have it as accurate as it came from the factory. Anyone that wants to take the time to learn and pay attention to details can do the same. I understand that everyone does not have a mold building shop with the tooling and measuring tools. A properly shimmed rod or main bearing is no different than it is after line boring. It is only quicker in 60 years to overhaul with less people to walk you thru the shimming.
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I forgot! I found it fun to measure the rods, rod bearings, crankshaft as well as all the parts to find in spec used parts rather than just buy new.






Edited by Dick L - 03 Sep 2019 at 3:18pm

Sooner or later, I'll probably rebuild the engine in my B.  It is 68 years old and as far as I can tell, the engine is as from the factory.  The last 30 years it has done light duty lawn mowing, but for the first almost 40 years, it lived a rougher life.  Money's not an issue, but I'm trying to figure out how I could expect "better" than the almost 70 years the original shimmed bearings have done.

DaveKamp wrote: Well... I'm certain it was a function of economics, but I don't think that representation is really accurate. I would venture an educated guess that they used shims in the first place, because it yielded a result that was appropriate for the combination of manufacturing economics, tooling systems, and consistancy in end results that they felt most appropriate. Align boring is a resource-intensive process, and keep in mind that resources include, but aren't limited to materials, manpower, or machinery... or TIME.    Shims DO have their benefits.

 The process used to line bore the block in the factory, wouldn't have been any different, with or without the shims. The block would have had the caps bolted up and bored to size either way, so I'm guessing it had to do with someones idea of who and where it might get worked on after a certain amount of wear in the bearings.

I suppose we could argue this forever! LOL

I don't know if that's a 100% true Curt. There are a lot of my customer's that still rely on their Tractors to make a living with because they don't want, (or can't afford) to go partners with the bank on a new piece of equipment that they can't even work on anymore! A lot of our customer's I talk with from all around the country (and out of this country) use their Tractors to make a living. Yup, there are a lot like you say to. Hobby guys (like myself) and folks that don't use their older Tractors so hard everyday like when they were new in the 40's n' 50's,  but they're out there. I've built a lot of wiring harnesses and rebuilt a lot of electrical components for customer's that still rely on their antique Tractor to do a certain job on their farm...

I have to side with Dick on this one. 

DaveKamp, Your sarcasm meter is defective. After buying an overhaul kit many do not have extra money laying around to put out three to four hundred into line boring, resizing rods or other costly items.

When I was into stock car racing with two little ones at home I headed home after stopping at the parts store. I looked over in the seat beside me and spotted a note my wife had given me that morning. It said stop and get two gallon of milk on the way home. I had spent all my cash and had to stop at a local store and charge the milk. That ended my racing dreams. Food and shoes for my little ones instantly became more important than the thrill of turning left in a cloud of dust in front of a grandstand of people hoping I would be taken away on a stretcher.

I assume people starting into old tractors have a passion with limited funds as I did.


Allis called out the shims as a way to get more life out of the engine. It was also used for that in the 1920's auto engines. All three of my 1920's Chevys have shimmed rods.

When I rebuilt Lena, the 35 WC, it had been rebuilt at least twice before and the main bores were not round at all. I put .006 shim in them and used a good Sunnen hone to make them real close to round. Everything cleaned up except maybe an 1/8 inch of the diameter right at the parting line.
 I had the crank ground and dropped new bearings in and it checked between .0025 and .003 with plastigauge and rolled over fine. I expect it to outlive me. It's only had maybe 100 hours on it since the rebuild .

Dick L wrote: That is how rich people do things. They used shims in the first place because they knew everyone was not rich! I line bored and resized the rods on my C for pulling. Been poor ever since. My old Chevys were shimmed also.

I'm definitely not rich!!!! Lol

That is how rich people do things. They used shims in the first place because they knew everyone was not rich!

I line bored and resized the rods on my C for pulling. Been poor ever since.

My old Chevys were shimmed also.

nella(Pa) wrote: I always plastic gauge my bearings to .0003. Never spun a bearing or had knock.

 I think you meant .003, that extra 0 would make it pretty darn tight

Dick. Even though you have a fresh ground crankshaft with matched bearings check each bearing with plastigage for clearance. Making sure the bearing is properly lubed and torqued, rotate the crank to make sure turns free before installing another bearing.   [/QUOTE wrote: X2 I always plastic gauge my bearings to .0003. Never spun a bearing or had knock. After I lubricate the sleeve and put on the o rings, I take a round screwdriver and slip it under the o ring and

Edited by nella(Pa) - 01 Sep 2019 at 11:33am

a "SHIM PACK".... is normally a few shims together that measure .006 inch... A PACK goes on each bearing cap bolt........ don't let the bearing touch the shim, just the CAP face.