 The Carter Thermo-Quad carburetor has float chambers manufactured of insulating plastic (phenolic), said to keep the fuel 20 degrees Fahrenheit (11 degrees Celsius) cooler.Usually, special vent tubes allow atmospheric pressure to be maintained in the float chamber as the fuel level changes; these tubes usually extend into the carburetor throat.Placement of these vent tubes is critical to prevent fuel from sloshing out of them into the carburetor, and sometimes they are modified with longer tubing.