Hey everyone...
Since the butterfly valve on a carb acts the same as on a throttle body, it creates a pressure drop,
and that lowers the temperature at the point of restriction. This is also known as "Carb icing".
From Wikipedia: (
https://en.wikipedia.org/wiki/Carburetor_icing)
Carburetor Icing, or carb icing, is an icing condition which can affect any carburetor under certain atmospheric conditions. The problem is most notable in certain realms of aviation.
Carburetor icing occurs when there is humid air, and the temperature drop in the venturi causes the water vapor to freeze. The venturi effect can drop the ambient air temperature by 30-40 degrees F (16.7-22.2 degrees C), therefore carburetor icing often occurs when the outside air temperature is in the 60-70 degree F (15.6-21.1 degree C) range.
In researching this episode I was also surprised to learn this.
