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1938 B

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=112720
Printed Date: 14 Sep 2025 at 8:31pm
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Topic: 1938 B

Posted By: acbnz
Subject: 1938 B
Date Posted: 01 Oct 2015 at 4:46am

Hello,I have recently come across what I believe is a 1938 ac B, serial # 10410.Apart from a badly leaking water pump everything else looks good.It has the six rivet front rims and is hand crank only.I suspect the block is not original as it has the two threaded holes for the generator to mount on and the engine serial number is R 24473 K which doesn't sound correct for this tractor to me.I wonder if the K in the engine serial number has anything to do with Kerosene,although the tractor has no small fuel tank or hole in the bonnet for that matter.If anyone knows what block this tractor should have or what the engine serial numbers on it relate to I would be very greatful,Regards Colin.

Replies:

Posted By: Ken in Texas
Date Posted: 01 Oct 2015 at 6:12am

The R prefix indicates the engine in your B is a 60H power unit engine. the K means Kerosene or dual fuel.
A correct block for a 38 with a late 38 SN would be a block with the casting number ending in a 10. The engine will have the engine SN BExxxxx stamped into the back of the block. No holes for a Genny bracket. Good luck finding a good early block. A early 39 #11 would be a alternative.
If you are lucky your B may still have a good set of Firestone rear rims original to your tractor. I will post a pic of the clamp used with these rims.
I helped a friend find all original early 38B parts for his restoration of B #751. I have a extra set of the early B wide seat back support springs for sale if anybody needs them.

Posted By: acbnz
Date Posted: 01 Oct 2015 at 6:16pm

Hello and thank you Ken for the information you have given me.I forgot to mention it but the engine that it currently has also has the oil feed going to the governor.The rear cast centre's where the valve goes is a u shape rather than a v shape which I understand is early style but I don't know about the rims as they do look in very good shape for a tractor of this vintage so I wouldn't really know if they were original or not.Going by the engine serial number of the present engine that you have identified as coming from a power unit would you have any idea of the year it may be from? I imagine it would be lateish since it has the governor oil feed on it.Would this be the 125 ci or some other capacity do you think and would the revs be increased on the power unit engine compared to the original 116 ci engine? Any info you may be able to supply about this power unit engine is very much appreciated,Thank you,Colin.

Posted By: Ken in Texas
Date Posted: 01 Oct 2015 at 9:54pm

About the wheels and rims. You have the correct early B wheels if they have the half moon notches instead of the V notch The bolt holes for the rim clamps should be for 3/4 bolts.
    From B501 up until B18055 the clamps used plain 3/4 bolts and eccentric 3/4 bolts. The rims for this period were not the standard rim used after B #18055 when the wheels used the new style clamps with 5/8 bolts.
   I can't help you much with the power unit questions except yours should have 3 3/8 pistons. The CR prefix power units were the latest ones after the R power units beginning with PU-53977 gas and PU-55480 dual fuel. More revs too. 1900 rpm

Posted By: acbnz
Date Posted: 08 Nov 2015 at 8:12pm

Well I finally got this tractor in my possession and have carted it home and can say I am very pleased with it.The engine runs very well no blue smoke at all,starts 3rd crank hot or cold 99% of the time.The tractor number,front and rear wheels and pto unit all indicate 1938,the last two engine casting numbers end in 20 which would make the block 1948 I believe,it also has 4 nuts holding the rocker cover on and an oil feed to the governor.With the help of the wife I tested the compressions and got between 75 and 80 on all four cylinders with 3 strong flicks on the crank handle-not sure if this is a good test but seems close enough to be a good sign.Both front tyres near new,rears 85% worn but in sound condition although they are fitted around the wrong way.Water pump leaking badly and will need replaced although you can run it and as long as the revs are up the water barely leaks out.The hood is from a power unit I guess as it still has two tiny little holes that the air intake brackets fixed to-it's had a hole made in the hood also to take a temperature gauge as I can see that this is not original as it's not quite a perfect circle.This tractor was repainted 20 years ago and has always been housed ever since.It has Allis Chalmers decal in black which would be wrong I think but is neatly done.It hadn't been used at all for many years as the old chap that owned it had another that was electric start and he preferred to take that to displays,unfortunately he has passed away and his family decided to move it on.l was fortunate to be able to purchase it and hope to be able to take it to local events.Not sure how to post a photo but when I work it out I will do so.

Posted By: Chalmersbob
Date Posted: 08 Nov 2015 at 10:28pm

Usually power unit hoods had a hole for the gas cap. Check the serial # of the engine near the air filter.

They used a squared off tank and it was installed with the fill closer to the engine.

My 48 C has a 2 bolt valve cover. LOL Bob

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4 B's, 1 C's,3 CA's, 2 G's WD, D14, D15, B-1, B10, B12, 712S,

Posted By: acbnz
Date Posted: 08 Nov 2015 at 11:29pm

Hello and thank you for your reply,I rechecked the engine serial number which is R 24473 K. The last two digits cast on the block just near the spark plugs is 20.I just guessed it might be a power unit hood because I saw two little holes about quarter inch diameter which I thought may have been for the brackets to hold a longer air cleaner intake? I have never seen one of these before so I really don't know.There is no hole for a fuel cap in the hood and it looks like the hood on my 1940 B,but no hole for a petrol tank.Clearly this block is not original to this tractor and quite likely the hood may be unrelated to either the tractor or the motor,I am greatfull for your help and hope someone may be able to shed some light on it, Thanks Colin. ps,was just thinking is there any way of determining what year the head might be from as this may not be original to the block either,I will be checking the tappets soon so if you know of a way to age the head I would be interested to hear.