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ROCHESTER CARBURETORS Bulletin 9D-8 August, 1951 |
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Bulletin 9D-8
August, 1951
Model "BC"
Page 5
ROCHESTER PRODUCTS, DIVISION OF GENERAL MOTORS, ROCHESTER, NEW
YORK |
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POWER SYSTEM
As shown in Figure 4, a vacuum
operated Power System is included in the carburetor to provide additional
fuel for sustained high speed operation or increased road load
power.
A direct manifold vacuum passage
within the carburetor to the engine intake manifold operates this system.
At any manifold vacuum above approximately 5" Hg., the power
actuating piston is held in the
"UP" position against the compression of the power spring by
manifold vacuum. As a consequence, no fuel passes through the ball type
power valve.
In accordance with the principle
that any sudden acceleration causes a drop in intake manifold vacuum, the
power spring has been calibrated so that at any vacuum below
approximately 5" Hg., it forces the power actuating piston
"DOWN", |
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Figure 4. Power System |
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The end of this piston then
unseats the spring-loaded ball in the power valve. Fuel passes readily
around the ball into the base of the Main Well Support. The calibrated
power restriction meters the fuel prior to its joining the fuel from the
main metering jet. Conversely as the manifold vacuum rises above
approximately 5" Hg., the power piston is drawn immediately to the "UP"
position, and the spring-loaded ball of the power valve closes, returning
the carburetor to the economical part throttle mixtures. There is no
adjustment required for the part throttle or Power
Systems, |
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The relief passage which is
drilled from the bore of the air horn into the power piston passage serves
to relieve any vacuum built up around the piston diameter. This vacuum if
unrelieved, would draw fuel past the piston and down the vacuum passage
into the manifold resulting in an overly rich
condition |
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