Chevrolet Light Operator's Manual page 26

This carburetor has a vacuum controlled power jet and a
throttle operated accelerator pump to aid in providing the
desired economy and performance.
Description-Updraft Carburetor. The updraft carburetor
used on. the Cab-Over-Engine and Forward Control trucks
is
mounted below the manifold. It
is equipped with
a vacuum
controlled power jet and a throttle operated accelerating pump
to aid in providing the desired economy and performance.
Care. Tighten the carburetor to manifold and the manifold
to cylinder head stud nuts to prevent air leaks. Keep the car-
buretor clean externally and have
it
completely overhauled at
regular intervals so that foreign matter in the carburetor and
worn
parts
will not affect correct carburetion.
' Ig. 27_Downd, ..
f,
C .. ,b ....
to,
Adj ..
.,men'
Maintenance - Downdraft
Carburetor. There are but
two adj ustments on the car-
buretor, one for idling
mix-
ture and the other for idling
speed. These adjustments
should be made together
as
changing the adjustment on
one affects the other.
Run engine until it
reaches normal operating
temperature. Push ch oke
knob
in
all the way. Turn
idling mixture adjusting
screw "A" (fig. 27) in (clock-
wise) as far
as
it will go and
then back it off
10/4
turns.
Let
engine idle at 450 to 500
revolutions per minute and turn idling mixture adjusting screw
"A" in or out as necessary to obtain a smooth idle.
Before adjusting the idling speed make sure the hand
throttle knob and choke knob are pushed in all the way and
that the accelerator and throttle linkage is free so that throttle
lever stop screw "B" (fig. 27)
is
against the stop. Turn screw
"B" in or out to obtain an idling speed of 450 to 500 revolutions
.".