B Cylinder pressures
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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=20142
Printed Date: 08 Feb 2025 at 10:47pm
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Topic: B Cylinder pressures
Posted By: Charlie175
Subject: B Cylinder pressures
Date Posted: 31 Oct 2010 at 12:20pm
What is the standard pressure test values?
Engine has good power and doesn't smoke except for a slight puff at startup.
I'm looking at some down time and was looking for things to do and working on the B is therapeutic. Thought about checking the bores getting the head checked. Might need my head checked since it runs good as is.
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Charlie
'48 B, '51 CA, '56 WD45 '61 D17, '63 D12, '65 D10 , '68 One-Ninety XTD
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Replies:
Posted By: Jeff Z. NY
Date Posted: 31 Oct 2010 at 12:29pm
If you get 125 you are doing good.
A slight puff of blue smoke at start-up sometimes is just some oil coming down the valve guides.
To do a good test get the engine hot.
Remove all spark plugs.
Gas shut off. I shut off the gas and let the engine drain the carb and stall before the test.
Choke and throttle wide open.
Air cleaner unhooked.
Give each cylinders around 6 revs for the test.
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Posted By: Coke-in-MN
Date Posted: 31 Oct 2010 at 12:30pm
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pressure isn't the important thing it isthe variation between cylinders that is . You can have loss of compression across all cylinders showing normal wear but when a large difference shows between them , problem needs to be found.
http://www.tractordata.com/farm-tractors/000/0/0/3-allis-chalmers-b-engine.html - http://www.tractordata.com/farm-tractors/000/0/0/3-allis-chalmers-b-engine.html
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Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful."
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Posted By: Jeff Z. NY
Date Posted: 31 Oct 2010 at 12:50pm
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Right, If you have 10-15 lbs differance between any cylinders it is time.
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Posted By: Charlie175
Date Posted: 31 Oct 2010 at 3:50pm
I split the tractor today to replace the throwout bearing only to find I was shipped a D12 bearing, the B is much smaller! Time to re-order.
I also removed the radiator as I had a slight drip from the upper neck, looks like the weld cracked. Need to find a local repair shop to have them fix it.
Cold I got 90 psi on 3 and 89 on 1. All the plugs look normal so no oil burning. My pressure gauge must be off as on my motorcycle it reads lower than normal also.
I also noticed the governor rod was hitting the belt drive and it had rub marks on it so I tweaked the rod a little to get it to clear. Now the carb goes from stop to stop with no interference. Maybe I will get full power now :) not that I thought it was lacking before.
I like the simple nature of this tractor!
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Charlie
'48 B, '51 CA, '56 WD45 '61 D17, '63 D12, '65 D10 , '68 One-Ninety XTD
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Posted By: Jeff Z. NY
Date Posted: 31 Oct 2010 at 4:12pm
They look ok. 90 is low but if you do it again with a hot engine you will see better reading.
Cold tests are always wrong.
The good thing is they are all equal.
Anything below 90 I would fix.
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Posted By: JimD
Date Posted: 31 Oct 2010 at 8:33pm
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That is a little low on compression. Not real bad, but wil make it a little harder to start and have a loss in power. Put some oil in the cylinders, and see if the pressure numbers come up. If so, the rings/pistons/cylinders are the problem. If not, the valves are suspect.
JimD
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Owner of http://www.OKtractor.com" rel="nofollow - OKtractor.com PM for an instant response on parts. Open M-F 9-6 Central.
We have new and used parts. 877-378-6543
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Posted By: CTuckerNWIL
Date Posted: 31 Oct 2010 at 8:42pm
Maybe you should have your head examined. LOL Now you done it Charlie. Ya got me thinkin I should check my B. Well it might not get done this year cause it's in the neighbors shed a mile away and the coolant has been drained.
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http://www.ae-ta.com" rel="nofollow - http://www.ae-ta.com
Lena 1935 WC12xxx, Willie 1951 CA6xx Dad bought new, 1954WD45 PS, 1960 D17 NF
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Posted By: Charlie175
Date Posted: 31 Oct 2010 at 9:08pm
it fires right up now, I can't imagine it being easier to start.
I'll check the valve settings as I'm sure they haven't been touched in years.
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Charlie
'48 B, '51 CA, '56 WD45 '61 D17, '63 D12, '65 D10 , '68 One-Ninety XTD
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Posted By: CTuckerNWIL
Date Posted: 31 Oct 2010 at 9:21pm
Mine too. Almost always on the second quarter turn of the crank, unless I forget to flip the kill switch to the run position.
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http://www.ae-ta.com" rel="nofollow - http://www.ae-ta.com
Lena 1935 WC12xxx, Willie 1951 CA6xx Dad bought new, 1954WD45 PS, 1960 D17 NF
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Posted By: Charlie175
Date Posted: 01 Nov 2010 at 6:15am
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How worn do you let the fingers on the pressure plate get worn down?
Oh and the bearing was toast but the clutch pack looks good.
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Charlie
'48 B, '51 CA, '56 WD45 '61 D17, '63 D12, '65 D10 , '68 One-Ninety XTD
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Posted By: Coke-in-MN
Date Posted: 01 Nov 2010 at 7:19am
10% variation is one sign of problems coming. Another way of checking is to use air into cylinder through spark plug hole , listen for air at carb for valve problems, breather for blow-by problems.
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Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful."
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Posted By: tractorkid1
Date Posted: 01 Nov 2010 at 8:29am
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I always liked using the cylinder leak down method insted of a compression gauge reading. The leak down test tells you more information as long as youlook and listen to where the air is coming out.
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Posted By: Charlie175
Date Posted: 01 Nov 2010 at 7:20pm
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Kudos to Scholtens Equip. I emailed them today about the bearing and they are overnighting me a replacement free of charge! Great service.
Now I have a 2.5" ID x 4" OD throw-out bearing if anyone knows what it goes to and can use it.
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Charlie
'48 B, '51 CA, '56 WD45 '61 D17, '63 D12, '65 D10 , '68 One-Ninety XTD
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