frosty carb

[andydap]

hi,
what cause the carb to frost up on a VAC and eventually quit?
andy

 

[kenbob]

Do you use gasohol? Not sure what the underlying cause is, but it certainly makes it worse.

 

[flatpkr]

It?s a normal thing, the Case SC does the same thing and probably many other makes and model?s. Possibly the fuel/air mixture being much colder than the outside air temp. Once engine heats up to operating temp. It goes away. About all I know about it.
Jim

 

[old]

That is the nature of how a carb works and is part of life and it they did not do that they would not work. Atomizing of the fuel causes the carb to get cold and that in turn can cause carbs to ice up. That is why older cars and truck had a hot air intake tube off the exhaust manifold to pull warm air into the intake. One can help that problem by making a side cover or some such thing to help keep the carb warmer. Or let ti run a bit longer so the manifolds heat up more before you work it

 

[tomturkey]

My VAC, SC, DC and 400 all frost up on occasion. It has never made them not run, and seems to melt off after a bit. Just the workings of an updraft carburetor. I always have believed the outside relative humidity levels played a role in this also. gobble

 

[r.w.b.]

I start my long throat manifold tractors,let them run no load quarter throttle couple minutes,shut em off for 4 or 5 minutes,restart and most every time they run ok not frosted up.lets heat come down that long throat

 

[L.Fure]

(quoted from post at 10:42:03 10/22/19) I start my long throat manifold tractors,let them run no load quarter throttle couple minutes,shut em off for 4 or 5 minutes,restart and most every time they run ok not frosted up.lets heat come down that long throat

That's the way I do it too. Cold damp days will cause this to happen. Another way is to warm up the engine as described in the operators manual. After starting the engine, and making sure the oil pressure is up, run the engine full throttle until the engine reaches operating temperature. Then put it to work.

 

[Bill(Wis)]

Air flowing through the carburetor venturi speeds up and then rapidly expands. "Expansion of a gas (air) is a cooling process". Something that used to be taught in school. It has been shown, in some carburetors, to cause as much as a 60 degree F drop in temp. That's why carburetor equipped aircraft engines incorporate some form of carburetor heat mechanism to prevent carburetor icing. The ice you observed on the outside of the carb will just as well form on the inside and can eventually choke off all of the fuel/air flow. Not good. We had a big Ford cabover truck that was famous for carb icing. Usually happened on 40 degree days with a good bit of moisture in the air. The way we kept it from happening was to use Mobil Super+ gasoline in it. It had sufficient anti-icing ingredients in it to keep ice from forming. (They call Mobil high octane gas "Super+" here in Wisconsin)

 

[kevinthefixer]

As the others said, it's normal, happens to almost anything with a carb. This is why the exhaust manifold is connected to the intake manifold, so the exhaust heat can warm the intake. This process can be sped up by shutting off the engine for a few minutes after the exhaust has heated up. Warming the intake air helps, too.