U Engine #
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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=124872
Printed Date: 18 Jul 2025 at 10:41am
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Topic: U Engine #
Posted By: 51ACWD
Subject: U Engine #
Date Posted: 21 Jun 2016 at 8:53pm
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Does anybody know what a U engine # of UM or UMA7601G denotes it as?just wanting to know the year maybe, and to see what fuel it took. It's in a 1936 U serial #12343
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Replies:
Posted By: everett048
Date Posted: 22 Jun 2016 at 1:31am
G for gas K for kerosene(distillit) hope that helps.
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Posted By: 51ACWD
Date Posted: 22 Jun 2016 at 7:11am
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They used letters K,G,H, and B on the U engines. K meant distillate 3,000 feet or below altitude. G was distillate between 3,000 and 6,000 feet and gasoline above that. All the letters were dual fuel, but they had different engines to run the most efficient at different altitudes
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Posted By: everett048
Date Posted: 22 Jun 2016 at 11:39am
Sorry but i think you have that wrong G & K are fuel types,Engines also had a A after the G OR K to denote if it was high altitude pistons or not.Compression was designated by either 3 or 4 types of pistons 1 of them being flat top the others being dished to different measurements for the compression ratio.Where as the A & K motors the wrist pin was moved up or down the piston depending on fuel type,(different piston types)
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Posted By: 51ACWD
Date Posted: 22 Jun 2016 at 12:07pm
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Even though my engine has the duel fuel tank, and dual fuel manifold?
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Posted By: 51ACWD
Date Posted: 22 Jun 2016 at 12:10pm
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What I am reading on the engine is that the G code had a 4.7:1 compression ratio. Gasoline was to be used at 3000ft or below and distillate between 3000-6000 feet altitude
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Posted By: 51ACWD
Date Posted: 22 Jun 2016 at 1:31pm
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Do you have any references I can read up?im not finding much out about the U's and just want to do some reading
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Posted By: everett048
Date Posted: 22 Jun 2016 at 3:54pm
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if it has the dual fuel tanks from new, it May have run on distillate with the exhaust in the middle and the K on the heat exchanger on the top side it may also have had the low comp pistons as well hence the engine n,o ending with a K. The pistons may have been replaced at some point with gas pistons.According to my DEALERS parts book piston part no 211658 with a 5/32 cupped top has a comp ratio of as you say 4.7-1 but how do you know what pistons are fitted?it could have part no 211657 cupped to 3/4 deep for kerosene.And i quote from the dealers parts book the letters UMA in a typical engine serial no such as UMA-25197K indicate that model of the engine while the letter K following the serial no indicates the the engine is equipped with pistons and other equipment necessary to use Kerosene as a fuel,If the letter G follows the serial no the engine is equipped to burn gas un quote.
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Posted By: CTuckerNWIL
Date Posted: 22 Jun 2016 at 4:10pm
I would think a compression check could tell you what fuel you can burn in your engine .
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Lena 1935 WC12xxx, Willie 1951 CA6xx Dad bought new, 1954WD45 PS, 1960 D17 NF
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Posted By: 51ACWD
Date Posted: 22 Jun 2016 at 4:11pm
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Weird. I know my manifold has BOTH spots on to change where my exhaust is ran at. Just a circular plate to cover which one is not being used. I am just simply asking. The engine has a FAINT A at the end of "UM" then under it has 7601G.
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Posted By: SteveM C/IL
Date Posted: 22 Jun 2016 at 7:05pm
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my UC has kerosene pistons and runs fine on gasoline with the plate flipped.actually (it's been a while) I think it outlets the exhaust at a different spot for gas and kereo
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Posted By: 51ACWD
Date Posted: 22 Jun 2016 at 8:50pm
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Mine has a plate on the side exhaust outlet and the exhaust dumps out the front under the hood. Has a spot for the dual fuel tank in the hood but is a G code engine. Why would it have the spot for a starting tank but have the g code for gasoline? And the manifold is a dual fuel manifold
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Posted By: everett048
Date Posted: 23 Jun 2016 at 1:37am
Almost all the manifolds were dual fuel except for the very early ones the first dual fuel one,s had a removable plate that you could either have in the front to run on low grade fuel or in the centre with a front exhaust to run on gas,they then changed to the next type witch you the exhaust was in the center and you just turned the plate to either G at the top or K at the top depending on fuel.As for the G on your engine no reread my previous post it is explained in that,Also your hood having a starting tank fitted was it original to the tractor? or has it come from another U as yours was damaged ? there is probably no way of knowing for sure.
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