This new engine speed governor has been designed and engineered as an integral part of the Holley Carburetor. The governor is a vacuum controlled device featuring all the advantages of a mechanical governor without resorting to lengthy and complicated linkage. The governor can be cleaned and serviced without the use of special tools.

The governor is made up of two units (See C). The control at the engine end of the governor consists of the governor valve (47), an adjusting screw (48) and a spring (49) assembled in a rotor (41) which revolves at one half the engine speed, in a housing (52) attached to an engine driven by the shaft (43). The controls at the carburetor end of the governor unit consists of a diaphragm (35) which is connected to the governor lever (45) by a short rod and a tension spring (46) which is also attached to the governor lever (45) and tends to hold the throttle open.

The diaphragm chamber (33) is connected to the governor valve air bleed orifice (50) by means of a conventional pipe line (34). The air bleed supply enters the rotor housing (52), from a pipe line (42) attached to the engine air cleaner or carburetor.

Vacuum to the diaphragm (35), is supplied by means of the two channels (37) and (38). (37) opens into the carburetor above the throttle plate and channel (38) below the throttle plate. These two openings are connected by channel (29) which in turn connects to channel (36) through the variable restriction (44).

OPERATION

When the engine is running at idling speed, the throttle is controlled by the external lever (25), and the pin (54) which is held against the internal lever (53) on the throttle shaft by the accelerating spring. At idling speed the governor valve (47) is held way from the air bleed orifice (50) by the spring (49) which is fastened to the governor adjusting screw (48). As the accelerator is moved to and held in the full open position to increase the engine speed, the governor spring (46) pulls the throttles to the wide open position to remain there until the engine RPM has reached the predetermined governor cut-off speed. At this point the governor mechanism which has kept pace with the engine speed is ready to go into action and take over control of the throttle, causing the acclerator system to become ineffective for further engine speed increase. The action of the mechanism is that when the engine speed increases, the governor valve (47) stretches the spring (49) and moves toward the air bleed orifice (50) thus restricting the bleed to the diaphragm (35). As the air bleed to the diaphragm is reduced it permits the suction supplied by the orifices (37) and (38) to operate the diaphragm. As this suction increases, the diaphragm power overcomes the tension of the governor spring (46) in and takes over full control of the throttles. The engine governed is then held constant by the valve (47) being balanced between the pull of centrifugal force actuated by the rotation of the shaft (43) and the tension of the spring (49).

Any slight change in speed or engine load will cuase the governor valve (47) to act immediately either to increase or decrease the amount of air bled through orifice (50), which in turn causes an instant response from the diaphragm to increase or decrease the throttle opening.

When the accelerator is released the control is taken away from the governor by the external throttle lever, and the connecting spring (46) then closes the throttle to bring the engine to any desired lower speed.

NOTE: The governor adjustments have been set at the factory to operate the engine at the proper recommended speed. It is not likely that the adjustments will change once they are set.

ADJUSTMENTS AND SERVICE HINTS

To adjust the governor cut-off speed, proceed as follows

1. Remove the seal from the screw (51) that will be found on the side of the governor housing (52).
2. Remove the screw from the housing.
3. Rotate the engine until the end of the governor rotor (41) which carries the adjusting screw (48) is in line with the hole from which the screw (51) was removed.
4. With a suitable screw driver, turn the adjusting screw to the right to increase the engine governor speed or to the left to decrease the speed.

NOTE: Where the governor has been disassembled and serviced, after reassembling, turn the adjusting screw (48) to the right until it stops then turn the screw to the left three full turns. Final adjustment is then made after the governor has been assembled to the engine as outlined in operation #4.

The vacuum adjusting screw (44) regulates the RPM spread between the governor full load cut-off speed and the no load engine speed. Turning the screw out or to the left will increase the spread.

NOTE: Changing the position of the screw (44) will change the average governor speed and this should be corrected by the adjusting screw (48) as outlined in operation #4.