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ROCHESTER CARBURETORS Bulletin 9D-9 January 1952 |
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Page 11 ROCHESTER PRODUCTS, DIVISION
OF GENERAL MOTORS, ROCHESTER, NEW YORK
CHOKE MODIFIER
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Figure 7-7 |
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Use Figure 7-7 as a
reference.
The choke system, as used on some
Model 4GC Carburetors also incorporates a choke modifier. The purpose of
this choke modifier, as required by certain engines is to prevent "loading
up" or excessively rich mixtures during the warm-up period.
Under normal operating conditions
the automatic choke assumes a position where the torque of the
thermostatic coil is balanced against the vacuum pull on the choke
piston plus the air velocity
against the offset choke valve. As the heat from the exhaust manifold
relaxes the tension on the thermostatic coil the choke valve gradually
opens. |
When the engine is started cold
and the throttle is opened considerably (such as in going up a steep hill), vacuum drawing heat to the
thermostatic coil housing through (1) may not be sufficient to heat and
relax the coil before some "loading up" takes place. The choke modifier,
being linked directly to the throttle by means of the throttle shaft
modifier lever (2), choke
modifier rod (3), thermostat modifier lever (4) and index plate (5) is actuated by the slightest
throttle movement. Thus the choke modifier lever rotates the thermostatic
coil, thereby relaxing the tension on the coil and allowing the choke
valve to open sufficiently to prevent "loading up." |
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