Thermostatically Controlled Air Cleaner
Carburetor air intake system consists of a heat stove, a corrugated paper heated air pipe and an air cleaner incorporating a temperature controlled door operated by vacuum through a temperature sensor. Operation is as follows:
- Heat stove is a sheet metal cover, shaped and bolted onto exhaust manifold. Air drawn in along lower edge of stove passes across manifold surface, picking up heat. Heated air passes through corrugated paper air pipe and enters snorkel of air cleaner.
- Temperature controlled air cleaner is designed to mix this heated air with cold air from engine compartment so that carburetor air temperature averages 115°F. Mixing is done by an air door located in snorkel. Most of the time, door will be partially open. When underhood temperature reaches about 135°F, door will close and will not allow any more warm air from manifold to enter air cleaner.
- Temperature door is moved by a diaphragm type vacuum motor. When there is no vacuum present in motor, diaphragm spring forces door closed. Whenever engine is running, amount of vacuum present in vacuum motor depends on temperature sensor in air cleaner, which is located in vacuum line between intake manifold and vacuum motor.
- Inside sensor, a bi-metal temperature sensing spring starts to open a valve to bleed more air into vacuum line whenever temperature in air cleaner rises above 115°F. At this temperature, sensing spring starts to close air bleed into vacuum line allowing more manifold vacuum to reach vacuum motor. Whenever there is 9" or more of vacuum in vacuum motor, diaphragm spring is compressed and door is opened.
- When starting a cold engine (air temperature under 85°F) air door will open immediately. This is because air bleed valve in sensor is closed so that full manifold vacuum is applied to vacuum motor. As soon as air cleaner starts receiving hot air from heat stove, sensor will cause air door to close partially, mixing cold and hot air as necessary to regulate air cleaner temperature within 20°F of the ideal 115°F air inlet temperature.
- While air cleaner temperature is being regulated, accelerating the engine hard will cause vacuum level in intake manifold and in vacuum motor to drop. Whenever vacuum drops below 5" of vacuum, diaphragm spring will close air door in order to get maximum outside air flow required for maximum acceleration.