 |
 |
10 of 35 |  |
 |
 |
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.
SPARK CONTROL VALVE
8. DASHPOT
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.
DAS
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
