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Farmall & IHC Tractors Discussion Forum
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1940 Farmall M --runs good but low horsepower.

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TYE W

12-12-2005 10:46:26




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Finally got the M running decent yesterday. It was running rough, not firing on cylinders 3 and 4 due to a manifold leak. Installed new manifold gaskets, everything seemed fine after that. Took it up and got it dynoed today. I was shocked -only 28 horsepower at the pto. I am pretty certain the tractor could use a valve job, adjusting etc. Timing could be off. This tractor supposedly had super M specs to the engine. This engine putting out 10 horses less than a factory stock M. Man, the lies people will tell you to sell a tractor... Sorry, just blowing off a little steam. --Tye

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captaink

12-13-2005 08:47:10




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 Re: 1940 Farmall M --runs good but low horsepower. in reply to TYE W, 12-12-2005 10:46:26  
A compression test is a good place to start. Depending on pistons (flat or stepped) and the head on your engine (kerosene, gasoline, or propane) the compression could range between 90 and 140+ psi. Even compression (within 10% of each other) means that there is even wear on the cylinders and even valve sealing. Fuel mixture and timing can affect horsepower dramatically as well as valve clearance. If you pull the valve cover to check the clearance, look for a casing number on the top of the head, this will tell you what head you have. Then some of the other gurus here can tell you more accurately what kind of compression pressure you can expect. The engine might have super M pistons but an old low compression kerosene head.

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El Toro

12-12-2005 16:17:38




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 Re: 1940 Farmall M --runs good but low horsepower. in reply to TYE W, 12-12-2005 10:46:26  
Are you sure the main jet adjusting screw is opened far enough? This is located near the bottom of the carburetor and I would open it several turns and see if your power improves. If this isn't opened far enough your engine may be running too lean. Hal



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P Backus

12-12-2005 11:45:44




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 Re: 1940 Farmall M --runs good but low horsepower. in reply to TYE W, 12-12-2005 10:46:26  
Yeah, I feel your pain on the misrepresented tractor sale. Leaves a bad taste in your mouth. However it sounds like you"ve got a good machine to work with. Maybe do that valve job ( at least check compression) and go through the ignition, timing, etc. and that M may come around real nicely. You"ll have more satisfaction knowing that you had a hand in bringing it back.
Paul



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TYE W.

12-12-2005 12:06:16




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 Re: 1940 Farmall M --runs good but low horsepower. in reply to P Backus, 12-12-2005 11:45:44  
Paul, Thank you for the reply. You wouldn't happen to know the psi amount for a compression test would you? Thanks for any help. -Tye



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P Backus

12-12-2005 12:25:47




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 Re: 1940 Farmall M --runs good but low horsepower. in reply to TYE W., 12-12-2005 12:06:16  
I don"t offhand, although someone else might. The old conventional wisdom is that all the cylinders should be within 10% of each other, ie readings of 90, 92, 88, 95 would be good, as opposed to 90, 92, 45, 95 psi. Usually if the valves are the culprit, one or two cylinders will be way low, as opposed to everything leaking evenly.
Hope this helps.
Paul



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