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vacuum drops below a predetermined point, the 
spring overcomes the reduced pressure on the 
diaphragm and closes the spark valve. Closing 
the spark valve prevents excessive spark retard.
As engine speed approaches the throttle set
ting, manifold vacuum increases and the spark 
valve opens, resulting in a higher vacuum to 
operate the distributor. In addition to preventing 
detonation when changing from part throttle to full 
throttle conditions, the intermediate spark ad
vance also avoids the sluggishness of wide-open 
throttle spark advance.
the closed or idle position, a tab on the throttle 
lever contacts one end of the dashpot lever, 
causing the head of the dashpot adjusting screw 
in the dashpot lever to press on the diaphragm 
stem. As the stem is moved into the dashpot, the 
tapered step of the rod engages the diaphragm 
washer. While the rod continues to move, it 
causes the diaphragm to move, thus compressing 
the air in the diaphragm chamber. The com
pressed air, bleeds out slowly from the diaphragm 
chamber through the passage in the diaphragm 
washer. This allows the throttle lever to close 
completely, and also retards the closing speed of 
the throttle plate.
Engines, equipped with automatic transmis
sions, use an anti-stall device called a dashpot. 
The dashpot affords protection against loading 
the engine when the accelerator pedal is suddenly 
released. The dashpot acts to retard the closing 
rate of the throttle as it approaches the idle posi
tion. This gives the engine time to dissipate the 
raw fuel discharged into the intake manifold, thus 
overcoming the hazard of stalling.
The dashpot slows down the final phases of 
the throttle plate closing by means of a spring
loaded air trap diaphragm. When the accelerator 
pedal is released, the throttle return spring, in 
the throttle linkage, acts to close the throttle 
plates simultaneously with the release of the ac
celerator pedal. As the throttle plates move to
When the throttle is again opened, pressure 
is removed from the dashpot diaphragm stem 
allowing the dashpot return spring to move the 
rod off its seat in the diaphragm washer. After 
moving the stem off its seat, the spring returns 
the rod and diaphragm to their original position, 
permitting air to flow back again into the dia
phragm chamber.
9. GOVERNOR - 2110-G
A Holley Centri-Vac vacuum-operated engine 
speed governor is incorporated in this carburetor 
as a positive means of controlling engine speed. 
The governor contains a throttle actuating mech
anism attached to the throttle shaft of the carbu
retor. The throttle actuating mechanism consists 
of a diaphragm assembly, governor spring, and 
governor lever assembly.
Below governing speeds, the operator, through 
a simple clutch arrangement on the throttle body
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