Carburetor Condensation

[Bill Lee/Virginia]

What is causing this?

I searched and could not find any info on carburetor condensation.

I am experiencing condensation on a downdraft carburetor on my Model A to the point it is actually dripping down on the engine pan. It must be dripping down into the carburetor since the engine is missing and running rough. This happened the other day in 90F and today in 80F temps. The liquid is actually cold to the touch.

Local gasoline does include alcohol. I add several ounces of MMO and SEAFOAM when I fill up the fuel tank.

This has not happened during the past 3 years in all temps driving from 30f to 100F.

I appreciate all info and advice.

Bill Lee/Virginia Peninsula

[Brian T]

Hello Bill,
It is not unusual to see a mild frost appear around the area outside the
Venturi on extreme humid days, it may have also began building up inside the carb around the throttle plate which may explain the rough running, odd that it hasn't occurred before.
Regards Brian.

[rocket1]

My early Chevy six and Olds use exhaust heat to alleviate this problem.

[nhusa]

It is called Icing. When a liquid vaporizes it gets cool - like an air conditioner.
The frost you see is the moisture in the air freezing on the cold surface.
Sometime it isn't cold enough to freeze but the surface just gets wet.

As Brian says the frost can build up inside the carb and change the air flow.

Aircraft pilots use carb heat to stop this from happening - to them

MY T has a tube that takes air from the surface of the exhaust manifold and directs it into the carb to help keep things warm and stop icing.

[tbirdtbird]

carb 'icing' as stated. Post a pic. Base of carb not getting enough heat from head or exhaust wherever it is supposed to get its heat from. I have actually seen the outside of a carb turn into a solid ball of ice from this. At that point all the fuel going into the cyls was pure liquid, black smoke poured out the pipe, and the car stalled. I wondered what was going on until I lifted the hood and looked at the carb

What happens when you spray a can of spray paint or computer air for more than a few secs? The can gets cold. An expanding gas absorbs heat (else it cannot expand). This simple statement is actually the refrigeration principle. If you kept spraying, dew would form on the cans and they would stop spraying because no more heat was available at that moment to vaporize the contents. Put the can down and come back later when it has warmed up and it will spray normal again.

Sometimes HVAC guys have to put their jug of refrigerant in a warm water bath to keep the 'freon' coming out if they are charging a big job

Computer guys keep a few cans of air laying around so that once the first one gets too cold to atomize they just move on to the next can. Later, when re-warmed, the first can again miraculously works fine

Amazing this has not already happened to you, unless something is now different

[marc hildebrant]

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What advantage do you get by using the downdraft over the original design ?

Marc

[Dave in MN]

Attached below is a photo of icing on a carburetor. Your condition is not as extreme as this shows...but under just the right conditions...it could happen.
Good Day!

[tbirdtbird]

yep, classic, good pic Dave

If you hold onto the Zenith throat when an A first starts up you will feel how surprisingly cool it is

[Duffy1]

This is a great thread . I was wondering why I had water on the base of my Zenith carburator. Ford Barn comes through when you do not even post a question .

[Tom Wesenberg]

Just run an air tube from the carb base to the firewall, and you will have free air conditioning!