Vacuum Vent Valve

Some engines which use the 2700 variable venturi carburetor require vacuum vent valves.

The thermactor vacuum vent valve provides the makeup air for the thermactor retard delay valve and air bypass valve during idle modes to deactivate the thermactor system after a controlled period of time.

Application of vacuum from the carburetor to both ports of the thermactor vent valve causes the diaphragm to initially move left and the dump valve to seat. With the dump valve seated, the vacuum is applied to the rest of the system.

The removal of vacuum during idle modes results in the diaphragm moving right. The dump valve leaves the seat, opening the vent and allowing air to enter the system to reduce the vacuum previously applied to the retard delay valve.