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Advisor

for you old farmall guys???

I have a 400 farmall that is a nice little tractor for augers and moving equipment. Problem is, it runs like crap anytime it is less than 50 degrees.  Carb and the intake manifold collar above it frost up like crazy. when it's warm out it just purrs, but this sucks. Any help would be appreciated. I've had new carb kits put it a couple times and am using gas with ethanol. (which probably doesn't help)  Putting something around the engine helps minorly, doesn't seem the reall answer. Any other suggestions beside wait 'til spring?

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14 Replies
Advisor

Re: for you old farmall guys???

 We had a massey 44 that did it below about 40 degrees.  As I remember we never did figure it out.  It would need a valve job quite a bit too.  The carb was updraft and sat right next to the engine.  Now that I think back it was the manifold that would freeze up.

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Frequent Contributor

Re: for you old farmall guys???

Some gas engines are prone to this in cold weather. The fix is to preheat the air before it hits the carb. Most of your old cars and trucks that had carbs used a snorkel that would draw heated air from a shroud of tin wrapped around the exhaust manifold. When they warmed up, a flapper door in the snorkel would switch to fresh (or underhood) air.I think that could be adapted to a 400 using automotive parts, but you might have to switch to a dry air cleaner and adapt or make a shroud to fit around the ex. manifold. Possibly you could suck warm intake air from a large pipe that you fit over the smaller ex. pipe, like the intake for modern corn and pellet stoves.. Most auto engines also used some water or exhaust heat in the intake manifold under the carb. That would help as well, but would be harder to adapt. The preheated air would not be good in hot weather, so you should swap back to fresh air when it is hot if you get vapor lock (boiling gas).

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Contributor

Re: for you old farmall guys???

We have a couple of old gas tractors that were the same way (farmall m and allis chalmers wd). The problem is the ethonal in the gas. Know that we started using ethonal free gas they run a lot better when its cold
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Veteran Advisor

Re: for you old farmall guys???

We have an old Farmall 350 (next series newer than your 400) so I am not sure they will be the same or not, but here goes:
On our old Farmall, the intake & exhaust manifolds run right next to each other.  There is a 'cold weather' valve between the two that allows heat from the exhaust to preheat the intake.  We had this valve rust and stick in the 'warm weather'  position.  This is operated by a weighted flap working against a bi-metal spring, and doesn't have a lot of force to overcome a rusted or sticky situation.  The mechanism is quite hard to see, with the weighted arm that actuates the flap in between the manifold and engine itself.  I can't even see it without removing the hood, but someone with skinny hands can reach between there  try to find it & work it loose. 

Keep in mind our tractor is the next series newer, and yours may not have this feature.

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Advisor

Re: for you old farmall guys???

thanks. that has to be it. i'll let you know.

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Contributor

Re: for you old farmall guys???

Nebrfarmr I believe you've nailed it.  My Super M (forunner of the 400) has that "heat riser" thingy. 

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Advisor

Darn ...

For once I knew the answer to someone's problem, and someone else answered first.

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Contributor

Re: for you old farmall guys???

well this is on our 560 but it too has the heat riser and I replaced that but what I had done to make it run much better was not just a carb kit but an electronic ignition.

It ran like crap before so had the dealer do the carb and added the electronic ignition and now runs great. huge improvement.

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Contributor

Re: for you old farmall guys???

I agree about the electronic ignition.  I've converted a couple of older gas tractors to 12 volt and Pertronix solid state ignition with the 40,000 volt Flamethrower coil.  The result is always an  instant-starting, smoother running tractor.  The distrbutor can be sloppy and worn and the electronic ignition could care less whereas with points the timing and dwell will be all over the place.  Just make sure your advancing mechanism moves freely and has good springs.  The original setup with points and the weaker coil neccessitates  fresh sparkplugs with square, clean electrodes with a gap around 0.022" to fire consistantly.  After the conversion, even worn sparkplugs set at 0.050" will fire beautifully.  The spark size  at 0.050" is humongous compared to the pityful spark that a 0.022" gap produces, and that large spark makes the combustion more likely in a less than perfect fuel/air ratio or in the aforementioned cold intake charge caused by an inoperative heat riser. 

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