Thermostatic Air Cleaner: Description
The thermostatic air cleaner provides heated air to carburetor (from shroud on exhaust manifold) when engine is cold, with progressive mixing of cold/heated air to maintain carburetor air intake temperature at about 105-130°F (41-54°C). At higher temperatures, hot air intake is closed off so that only underhood air is supplied to carburetor.
Mixing of air is controlled by a vacuum operated motor on air cleaner snorkel. When engine compartment temperature is below 105°F (41°C), bimetallic sensor in air cleaner assembly is closed and allows vacuum to pass through sensor and close door to engine compartment air. Warm air is drawn from around exhaust manifold shroud and into carburetor.
When temperature inside air cleaner reaches 105°F (41 °C), bimetallic switch opens and bleeds off vacuum. Without vacuum, the hot air door is shut and carburetor receives air from engine compartment.
The cold weather modulator valve, inserted in vacuum line between bimetallic sensor and vacuum motor, prevents vacuum override of air cleaner door at temperatures below 55°F (13°C) by maintaining vacuum at vacuum motor.