When anything, including gasoline, evaporates, it consumes heat. The venturi area of the carburetor, where the fuel vaporizing starts, is acting like a small refrigerator. From there to the the throttle plates, the temperature can drop enough to freeze the moisture in the air, inside and out, particularly when the temperature of the incoming air is close to freezing and the humidity is high. Airplanes have a "carburetor heat" system to draw air past the exhaust before it enters the carb to prevent carburetor icing and possible engine stalling. Modern automobiles have a similar system, where the air is pulled through a sheet metal shroud around the exhaust manifold during warmup, and redirected away from the heat after the inlet air temperature rises. The small accordion-pleated hose that is attached to the intake snorkel is the hot air source during warmup, and there's a flapper valve in the snorkel to swap over to cold air when necessary.
Jerry
Last edited by Hotrod Lincoln; 11/29/2009 4:44 PM.
