1930 Cadillac Brochure Front Cover - GM Heritage Center

The button must also be left out far enough during the warmingup
period so that the engine will run without missing and
"popping back."
On the other hand, it should not be pulled out any further or
left out any longer than is necessary to accomplish these results,
because some of the excess liquid gasoline in the enriched mixture
does not burn and washes off the oil on the cylinder walls, interfering
with proper lubrication of
the pistons. Push the button all
the way in as soon as this can be
done without causing "poppingback."
Fig. 4. The choke button must
be held out while the starter is
cranking the engine.
If the engine still retains heat
from previous running, the choke
control should not be used without
first attempting to start the
engine on the normal mixture.
If the choke button is pulled out
for starting a hot engine the
mixture may be made so rich that starting will be impossible.
The choke button is not a priming device. It has no effect
whatever on the fuel or the fuel mixture unless the engine is
being cranked or is running under its own power. To have
any effect, the button must be pulled out and kept partly out
during the cranking operation.
Spark Control
Correct timing of the ignition in relation to the positions of
the pistons is controlled automatically by the timer-distributor,
which provides for all ordinary advancing and retarding of the
spark.
A hand control is also provided. This is the button at the left
on the instrument panel. This button should be pushed all the
12]
way in (full advance) for starting and for all ordinary driving.
The button can be pulled partly out to retard the spark in case
of "ping" caused by carbon, heavy pulling, the use of regular
(not anti-knock) gasoline, or in case there should ever be occasion
to crank the engine by hand.
The Cadillac engine is a high compression engine and it will
perform most satisfactorily when an anti-knock fuel is used.
Regular gasoline can be used, although this may necessitate
driving with the spark slightly
retarded to avoid "ping." The
spark should be retarded just
to the point where the engine
"pings" slightly on rapid acceleration.
This slight amount of spark
knock is absolutely harmless to
the engine and is an indication to
the driver that the spark is set Fi & . j. Drive with spark control
as
at the point that will give max-
far *A v