1935 Cadillac - GM Heritage Center

132
GASOLINE SYSTEM
Fig. 14. The thermostat in the semi-automatic choke
on Cadillac cars should be adjusted by loosening the
adjusting nut and sliding the thermostat stop until
the required pull as indicated to hold the arm in a
horizontal position is obtained
Proper adjustment of the carburetor and choke
controls should prevent any possibility of popping
back in normal acceleration or deceleration. In
case of continued popping back with the carburetor
and the choke controls properly adjusted, the
cause will usually be'found in the contact points or
in the ignition timing. In retiming the ignition,
the flywheel timing indicator should be set on or
slightly ahead of the IG/A mark. It should not
be set behind the IG/A mark nor any more than
}/% in. ahead of the mark.
2. Equalizing Carburetor Adjustment—
370-D and 452-D
The adjustments of the two carburetors on the
370-D and 452-D cars should be equalized to
secure smooth running of the engine. The best
method to follow is to use an equalizing gauge.
The gauge is connected to the intake manifolds
after both the brake assister and vacuum lines
are disconnected. The throttle rod must also be
disconnected from the right-hand carburetor.
A preliminary adjustment of the metering pins
and throttle on both carburetors is then made to
bring the idling speed at approximately 320
R. P. M.
To determine whether or not the engine is
running at the correct idling speed, remove the
oil filler cap from one of the valve covers and hold
a finger on one of the valve rocker arms so that
the movements of the rocker arm may be counted.
At 320 R. P. M. the valve will open forty times
in fifteen seconds.
Make sure that the gauge hangs straight and
check the level of the mercury in the tube. When
the metering pins and throttle stop screws are
properly adjusted, both columns of mercury
should be at the same height and the engine
should run'smoothly at 320 R. P. M.
If the columns of mercury are not at the same
level and the engine speed is too fast, reduce the
speed by backing off the throttle stop screw on
the side on which the mercury column is the lower.
If the speed is too slow, turn the throttle stop
screw in a little on the side on which the mercury
column is higher.
If the mercury columns are at the same level
and the engine speed is too fast or too slow, adjust
both throttle stop screws, turning them exactly
the same amount to secure the correct idling
speed, at the same time keeping the mercury
columns at the same level.
Re-check the metering pin adjustments and
idling speed on both carburetors, making sure
that the mercury columns are maintained at the
same level.
Adjust the right-hand throttle control rod to
exactly the right length so that the clevis pin
can be slipped into place without changing the
engine speed.
A further check should be made on the throttle
adjustment by running the engine at approximately
1000 R. P. M. and noting the mercury
level in the gauge. If the columns are not practically
level, a slight readjustment of the righthand
throttle control rod will be necessary.
Finally run the engine again at idling speed and
check the mercury columns again. A very slight
readjustment of the throttle control rods may be
necessary to bring them to the proper level again.
If an equalizing gauge is not available, the
following method may be used to equalize the
carburetor adjustment.
Disconnect the coil wire for the right-hand
cylinder block. Adjust the metering pin of the
left-hand carburetor in the same manner as when
using mercury tube and set the throttle stop
screw so the engine will just turn over without
stalling.
Then disconnect the coil wire for the left-hand
cylinder block and adjust the metering pin and
the stop screw on the right-hand carburetor in a
similar manner.
With the metering pins and throttle stop screws
on both carburetors properly adjusted, the engine
should idle at about 320 R. P. M.
Inasmuch as some air is drawn into the manifold
of the carburetor being adjusted through the
vacuum brake assister connection on the opposite
intake manifold, the foregoing adjustment will
probably be slightly rich when all cylinders are
operating. To correct this, it may be necessary
to screw up slightly each metering pin adjustment.
This can best be checked by listening to exhaust
and making final adjustment with both sides
firing.
When a satisfactory adjustment of both carburetors
has been secured, adjust the length of the