Farmall M won't run at 180 psi compression

LarryM · Sep 11, 2009

I have an M with 180 psi compression. Today I put Autolite 386 plugs in it, Petronics Electronic ignition, New Wires, 45,000 volt coil, and I have 93 octane in it. What it is doing is that if I start it cold and dyno it the horsepower goes right up above 60 and then tapers off in about 30 seconds and the hotter the engine gets the worse it runs. 180 psi of comnpression is a new thing for me. We used to run a WC Allis with 170 psi on 93 octane just fine. When I dyno the M she starts out strong and then just starts missing and carrying on. I have tried a different carb. I have tried a different manifold. Manifold is sealed properly. The distributor is nice and tight. The valves are set at .020. I just ground the valves and lapped them properly. Valve guides are nice and tight. The darn thing will start without choking it when it is cold. Runs great until I work it on the dyno. I really need help on this.

the tractor vet · Sep 11, 2009

Check total advance timing DO NOT GO OVER 28 DEGREES at wide open throttle open the load screw up five turns and see what ya have then , ya may need to trick out the carb and give her more air and fuel . I am not having any problems with one that is pushing over 195 on a stock ing . system and 93 gas and she will dyno well over 80
And my self i am not a big fan of them electroinic ing. systems . I can change a lot of points before it makes up the cost of one of them and if a set of points does go bad in the field i can always nurse it back to the barn and put a new set in and be back to work in fifteen min .

rustyfarmall · Sep 11, 2009

Check the valve gap settings again. They are probably too close, and when the engine gets warm the gap goes away, in effect preventing the valves from closing fully. 0.017" with the engine hot. 0.020" with the engine cool.

LarryM · Sep 11, 2009

I did everything you recommend before posting here.

Anonymous-0 · Sep 11, 2009

get a colder plugs

Roger in Iowa · Sep 11, 2009

At 180 psi you must be running about 12.25 to 1 compression ratio. Better get some 110 octane av gas. I don't believe 93 is going to do the engine any good.

james rumph · Sep 11, 2009

I have 220 psi per cylinder and that is only 10.750 to 1 compression.

In your intake manifold tap a small hole for a vacume gauge. Under full load "on dyno" it should read almost zero. If it is produceing vacume then your running lean and it needs more fuel.

Do you have a fuel pump on it or is it still gravity feed ?

You are on the verge of race fuel and it wouldn't hurt , don't use A/F gas it has antifreeze in it.

Set your timing on the dyno under full load , go for highest rpm under load. We use a digital timing light with a tach in it.

Email me direct if you have any more questions, i run a dyno service.

Anonymous-0 · Sep 12, 2009

Needs more octane. Go get 5 gallons of E85, and 5 gallons of 93, pour the two cans of fuel in the tank and retune. If the head hasnt been tightend down correctly, the head will float from the nuts being loose when it warms up, and the valve lash setting will tighten up and loosen up, holding a valve open, just enough to lose cyl pressure. This engine will need a #29 venturi, OR, a W9 carburator would do it a world of good. Hope this helps. ChadS

Farmall M won't run at 180 psi compression

LarryM

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the tractor vet

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rustyfarmall

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LarryM

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Anonymous-0

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Roger in Iowa

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james rumph

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Anonymous-0

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