The model 1901-FFG truck carburetors incorporate the Holley Centri-Vac vacuum operated engine speed governor. The governor consists of two units, a throttle actuating mechanism which is attached to the throttle shaft of the carburetor and a controlling unit which is an integral part of the Holley pressure distributor and is driven by the distributor drive mechanism of the engine. The throttle actuating mechanism consists of a governor spring and a diaphragm which is exposed to carburetor vacuum. The spring and diaphragm are linked together by the governor lever which is attached to the throttle shaft of the carburetor. The controlling unit consists of a rotor which is driven by the distributor drive mechanism and contains a centrifugally operated governor valve.
