Cadillac
on the carburetor body, the tip of the air valve should, at a room
temperature of 65° to 85' F., have an opening of 1/64" to
1/32" when held up lightly.
In making this test do not apply enough pressure to the valve to
spring the thermostatic member to which the rear end of the air
valve spring is attached and against which the valve strikes when
the lever is held forward.
If the opening under these conditions is more or less than the
limits given, a readjustment may be made after removing the cover
(1) (Fig. 5), (see below under "Caution") and loosening
the two screws which hold the bracket carrying the thermostatic
member. Tighten the screws after completing the adjustment.
Caution: Care must be used in removing the cover (1) (Fig. 5) over
the auxiliary air valve not to ruin the air valve spring by stretching
or twisting it.
Remove the spring after lifting the cover just enough to permit
doing so. If the spring is deformed by careless removal of the
cover, do not attempt to repair it, but replace it with a new spring.
The tongue (4) (Fig. 3) should stand in the center of the slot
in the lever (3) when the carburetor enriching button on the instrument
board is forwar.l as far as it goes.
If the tongue does not stand in the center of the slot, a readjustment
should be made by altering the length of the control rod attached
to the lever (3).
Adjustment of Auxiliary Air Valve Spring
The rear end of the auxiliary air-valve spring is attached to a
thermostatic member which automatically adjusts the spring to compensate
for changes in temperature. The auxiliary air valve spring, therefore,
very rarely requires readjustment.
Before attempting to adjust the auxiliary air valve spring make
certain that the enriching device is in correct adjustment and
that the relief valve over the air valve seats properly.
The adjustment of the auxiliary air-valve spring is made by the
adjusting screw (5) (Fig. 3) and in the same manner as on earlier
eight-cylinder carburetors.
To determine whether the spring requires re-adjustment and to make
the readjustment, proceed as follows:
Start the engine and run it until the intake manifold is up to
normal driving temperature.
Place the spark lever in the fully retarded position and move the
throttle lever to the closed position. The engine speed should
then be about 300 revolutions per minute.
If it is necessary to adjust the throttle stop screw, proceed as
described under "Adjustment of Throttle Stop Screw."
After these preliminaries, make the following test to determine
the necessity for adjusting the auxiliary air-valve spring:
Press down gently on the ball-shaped counter-- weight of the auxiliary
air valve and note whether the immediate result is an increase
or a decrease in engine speed.
Release the counterweight and allow the engine to run a few seconds
to regain its normal speed. Then press up gently on the counterweight
and note the effect on the engine speed.
If the mixture is correct, the immediate result of gentle pressure
either up or down on the counter-weight of the auxiliary air valve
will be a slight decrease in engine speed.
If the immediate result of gentle upward pressure on the counterweight
is a slight decrease in engine
Fig. 5. Removing auxiliary air valve.
speed, while the result of downward pressure is an increase in
engine speed, a rich mixture is indicated.
If the immediate results of upward pressure is in an increase of
engine speed, a lean mixture is indicated.
If the above tests indicate an incorrect mixture, adjust the auxiliary
air valve screw (5) (Fig. 3) by turning it clockwise to correct
a lean mixture, and counter-clockwise to correct a rich mixture.
Continue to change the adjustment of the screw (5) and to test
as above until a correct mixture is indicated.
Do not turn the screw (5) more than a few notches at a time and
not more than two notches at a time when nearing correct adjustment.
Move the throttle lever to the closed position unless it is already
in that position. The engine should now run at a speed of about
300 revolutions per minute.
If it does not, change the adjustment of the throttle stop screw
(2) until this speed is obtained.
When the stop screw (2) has been adjusted correctly lock the adjustment
and adjust the collar on the control rod from the steering gear
so that the throttle in the carburetor will start to open immediately
the throttle lever is moved.
Test the correctness of the mixture as before, and if necessary
readjust the screw (5). When the test indicates the correct mixture
with the throttle lever at the closed position and the engine running
300 revolutions per minute, adjustment of the auxiliary air valve
spring is correct.
The adjustment of the enriching device should then be checked again.
Throttle Pump Adjusting Screw
This adjustment is provided to make it possible to lessen the effect
of the throttle pump which may sometimes be found desirable during
warm weather, or during cold weather, if high test gasoline is
used.
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