SC Case Carburator icing.

After running well for 10 minutes my carb on my 1949 SC begins to freeze and starts running poorly. It has white frost on the intake near the carb. This problem showed up after I did a valve job. Could that have anything to do with it?

(quoted from post at 08:43:28 03/26/19) After running well for 10 minutes my carb on my 1949 SC begins to freeze and starts running poorly. It has white frost on the intake near the carb. This problem showed up after I did a valve job. Could that have anything to do with it?

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Carburetor icing is fairly normal on some engines in damp weather. If you can find a way to warm the intake air source it will help. My brother runs a piece of pipe from the air intake to the exhaust manifold on the Wisconsin V4 that powers the wood saw.
Usually if a carb ices up it can be cured by shutting off the engine and letting residual engine heat warm the intake and melt the ice. After that they work fine. At least thats how it works here in Sask.

Carb icing happen to any and all carbs at times and is a fact of life due to atomizing of the fuel. That is why years ago car and trucks have the hot air intake tube coming off the exhaust manifold to heat the intake air to keep the carbs from icing. Simple way to stop it is to make a side cover to hold engine heat in on the carb side to keep the carb and intake manifold warm

That icing is common on those
old cases and shouldn't hurt
anything. If the icing is just
some light frost for a few
inches above the carb it is
normal. If it gets thick or
covers the whole intake then
you have an issue. If it is
normal levels then I would
look elsewhere for the
problem. Here is a pic of my
DC running.

You could make one something like this and you won't have that problem. This one is a piece of stove pipe and water pipe. If you wanted it lighter use exhaust tube instead of water pipe.

Carb frosting is normal in colder/cooler weather. So the mere fact of that, doesn't indicate a problem. How ever,
a rich fuel mixture, or excessive or unescisary choking might aid in the amount of frosting.

That said, I think you got an unrelated problem. Unless just by chance your carb fuel mixture got altered during
your valve job. But you shouldn't of had to do anything to the carb adjustments during a valve job. Did tractor
have this same problem before valve job?? Are you sure valve clearance is adjusted right? Hense causing engine to
run rough once warm. Most procedures for valve clearance, calls for adjusting while cold, and then re-checked
after engine has run to running temperature.

(quoted from post at 18:08:48 03/26/19)

That said, I think you got an unrelated problem. Unless just by chance your carb fuel mixture got altered during
your valve job. But you shouldn'

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Wouldn't the fact that a valve job might increase manifold vacuum have an effect on the carburetor adjustment?

I used to hang a curtain on the side. From the radiator,to just beyond the carb.

I agree, an oldtimer told me the same thing about my DC4, let it warm up, then
shut it off,carbs warms up,frost is gone and then its good to go.

I hardly think the valve job caused this icing up. but since you have more vacuum with good valves it might be more noticeable , maybe?? this happens because the air is forced through the venture of the carb and looses pressure and the air speeds up. this causes a drop in temperature and cause the moisture in the air to freeze. all carburators do this and is noticeable on the updraft carbs. if it has a carb it will have a cooling effect. its not just one make or type of tractors , they ALL do that. I have seen the carb get ice on it in july. this icing is called the "venture effect" perfectly normal . don't use it at wide open throttle till the engine warms up.

Lesson #1: "VENTURI" "A short tube with a tapering constriction in the middle that causes an increase in the velocity of flow of
a fluid and a corresponding decrease in fluid pressure and that is used especially in measuring fluid flow or for creating a
suction -as for driving aircraft instruments "OR DRAWING FUEL INTO THE FLOW STREAM OF A CARBURETOR". (The caps apply to your
situation).
Lesson #2: "EXPANSION OF A GAS IS A COOLING PROCESS".
Lesson #3: Fuel air mixture travelling through the venturi section of a carburetor can cool as much as 60 degrees F.
Lesson #4: On a 90 degree day you could cool the fuel air mixture down to 30 degrees F and if sufficient moisture is present it
could form ice. CARBURETOR ICE, NOT FUEL LINE ICE!!!
Lesson #5: What are you going to do? To prevent carburetor ice, you could incorporate some sort of carburetor heat device. OR,
YOU COULD BUY SOME GAS WITH A SPECIFIC CARB ICE PRVENTATIVE. We found, on an old Ford cabover truck with a habit of forming carb
ice (at about 40 degrees and a foggy, rainy day) we could prevent carb ice by using Mobil Supreme gas. It had an anti-icing
additive which worked for us. Don't rely on 10% ethanol. It probably won't be enough. Or, try some anti-icing additive in the
gas-which goes through the carburetor. Right?

Hey,I got one just like that. Its for sale but dont know what to ask for it. any ideas?

Here is a pic

What year? Foot clutch and eagle hitch?

Always preferred cream cheese icing over carburetor icing.