Cadillac 1933 V8 Operator's Manual page 151

G A S O L I N E SYSTEM
73
G e n e r a l
The general arrangement of the gasoline system
is the same o n a l l cars. T h e 370-B a n d 452-B
system differs slightly however, as each of these
cars has two carburetors.
The gasoline line from the rear supply tank
is mounted outside of the frame where the air
sweeping by tends to cool the gasoline and thereby
prevent the possibility of vapor lock. Sharp
bends and low spots i n the fuel line have also been
eliminated by running the line as nearly straight
as possible from the tank to the fuel pump.
C A R B U R E T O R
The 345-B a n d 355-B carburetors are of the
same general construction t y p i c a l of those used
on previous car models and the method of adjust-
ing is the same on both models.
The 370-B and 452-B carburetors are of the
expanding air v a l v e type. T h e y are simple i n
construction w i t h no thermostats and have only
one adjustment, which controls the mixture by
v a r y i n g the flow of fuel rather than the air.
The carburetors used on the 370-B a n d 452-B
are identical w i t h the exception of the size of
the metering p i n . A N o . 10 metering p i n is used
in the 370-B carburetors and a N o . 12 in the 452-B
carburetors. Otherwise the carburetors on these
car models are fully interchangeable. R i g h t and
left carburetors differ in the control levers. The
name plate m a r k i n g identifies the type of carbur-
etor; 370-B carburetors are T y p e R-13 a n d L - 1 3 ;
452-B carburetors are T y p e R-14 and L-14. T h e
carburetor consists chiefly of two units, namely,
the main metering unit a n d the auxiliary unit.
The main metering unit consists o f a pair of
air valves or vanes, hinged at their lower ends
and opening upwards to admit air to the mixing
chamber. These vanes have fingers which engage
a central aspirating tube, raising it as the vanes
open. T h i s aspirating tube is attached to a
spring loaded hollow stem and piston working in
a dashpot, the piston carrying the fuel metering
orifice in its lower end. A n adjustable tapered
metering pin projects into this orifice.
The auxiliary unit combines an auxiliary
power jet, an accelerating pump, and a priming
passage for starting. T h e operation of the auxili-
ary unit is controlled by the registering of ports
in the starting sleeve, which line up with passages
in the throttle body. T h e starting sleeve rotates
with the starting lever (choke lever) and the
i o n
p u m p plunger and piston move d o w n w a r d as the
throttle is opened.
O P E R A T I O N
For normal running the fuel enters the carb-
uretor float bowl through the strainer and float
needle valve, and is maintained at constant level
by the float and float needle valve. This level
of fuel should be to y§ i n . below top of float
bowl casting.
A i r enters the carburetor through the air inlet
and lifts the vanes as it passes upwards into the
m i x i n g chamber. T h e weight'of these vanes com-
bined w i t h the pressure exerted by the dashpot
spring causes a partial v a c u u m to exist in the
m i x i n g chamber, which draws fuel from the
aspirating tube. T h e q u a n t i t y of the fuel flowing
is controlled by the tapered metering p i n ; at idle
speed the vanes are almost closed a n d the metering
pin almost fills the orifice in the air valve piston.
A s the vanes rise to a d m i t more air, the aspirating
tube also rises and the metering orifice becomes
larger due to the taper on the metering pin. T h i s
combination maintains the correct ratio of fuel
and air for average running.
F o r maximum power at any speed a richer
mixture is required t h a n is necessary for part
throttle running. T h e power jet supplies the
required extra fuel while the throttle is held open
beyond the point which w o u l d give a road speed
of about 60 miles per hour. A t this throttle
position the pump plunger has travelled downward
and has shut off the air vent to the power jet,
therefore, the suction on the discharge nozzle
draws fuel from the p u m p cylinder up through
the hollow stem of the p u m p plunger a n d through
the power jet into the m i x i n g chamber.. A t part
throttle positions below 60 miles per hour road
speed this power jet does not s u p p l y fuel since it
is vented to the outside air through the air vent
hole in the upper part of the s t a r t i n g sleeve.
The quantity of fuel d r a w n from the power jet
is controlled by the air bleed hole i n the p u m p
plunger stem.
For rapid acceleration it is necessary to supply
a momentarily rich mixture. T h i s extra fuel is
supplied by means of the accelerating pump.
A rapid opening of the throttle causes a rapid
downward movement of the p u m p plunger and
piston, forcing fuel up through the hollow stem
ol the p u m p plunger and out through the discharge