Thermostatic Air Cleaners -- All Models: Description
All passenger cars use a system for preheating the air entering the carburetor. This device is part of the air cleaner and maintains the air temperature at a point where the carburetor can be calibrated much leaner to reduce hydrocarbon (HC) emissions and also improve warm-up operations and reduce carburetor icing.
System consists of an air cleaner assembly, integral air control door, vacuum control temperature sensor, vacuum motor(s) or thermostatic spring, heat shroud (on exhaust manifold) with heated air tube and vacuum hoses. Some models use additional controls, such as vacuum traps, cold weather modulators, vacuum check and vacuum delay valves.