Chevrolet with Old Carter Carburetors : CHEVROLET TRUCK 1940 1941 1942 1943

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CHEVROLET TRUCK 1940 1941 1942 1943

CHEVROLET TRUCK 3875-5185-518SA
February, 1940 Reprinted November, 1944
Form 6431 D—Canadian
DEPT. OF NATIONAL DEFENCE
SPECIAL VEHICLES ONLY


CHEVROLET TRUCK 1940 1941 1942 1943


387S Superseded by 518SA)
Casting No. 329 on face of flange.
Cut Shows 387$
DOWN-DRAFT CARBURETERS Nos. 387S-518S-518SA—LIST PRICE $17.65
A $2.50 exchange allowance is' deducted from the list price if buyer turns in old carbureter.
CARBURETER SPECIFICATIONS

For Chevrolet Six Engine:
Dimensions: Flange size, 1¼ inch S. A. E. Primary venturi, 11/32 inch I. D.
Secondary venturi, 11/16 inch I. D. Main venturi, 1¼ inch I. D.
Float Level: Distance from float (at free end) to float chamber cover to be 3/8 inch, plus or minus 1/64 when needle is seated.
Vents: Outside, none. Inside (balance vents) above choke valve through shaft, size No. 27 drill. Below choke valve, No. 35 drill.
Gasoline Intake: Square vertical needle. No. 48 drill size in needle seat.
Low Speed Jet Tube: Jet size, No. 72 drill.
By-pass in body, size No. 56 drill.
Economizer jet: size .059 to .060 inch diameter.
Idle passage bleed, into bore, above port; size No. 54 drill. Idle Ports: Upper port diameter, No. 44 drill. Lower port diameter, No. 52 drill.
Idle Port Opening: (387S-518S) Top of lower port .034 to .038 inch above top edge of valve, with valve tight closed. (518SA) .016 to .020 inch.
Idle Screw Seat: Size No. 50 drill.
Inch Bore, 3% Inch Stroke

Idle Adjustment Screw: Set one turn to two turns open. For richer mixture, turn screw out. Do not attempt to idle engine below 350 r. p. m.
Slip Nozzle: In primary venturi, angle 30°. Discharge jet size, .125 inch diameter.
Screw Nozzle: (Seats in slip nozzle) Jet: Size No. 31 drill.
Metering Rod: Economy step, .064 inch diameter; middle step tapers from .058 to .053 inch diameter; power step, .039 inch diameter. Length, 3% inches.
Metering Rod Jet: Size, .094 inch diameter.
Metering Rod Setting: Use gauge (Part No. T109-25) 2.795 inches.
Accelerating Pump: Low pressure type, with adjustable stroke. Discharge jet, size No. 72 drill.
Intake disk check plug, size No. 62 drill.
Discharge disk check plug, size No. 40 drill.
Choke: Manual—butterfly type, split valve.
Vacuum Spark Ports: (387S-518S) Upper port: Size No. 50 drill. Lower port (Enters bore on angle): Size No. 56 drill. (518SA) Slot type, .041 x .125 inch. Bottom of port .000 to .004 inch above valve.
Correct Float Level
(Remove Cork Gasket
and measure from
machined surface of
float cover)
% Inch
NOTE ON VALVE ADJUSTMENT. It is important that valves be adjusted with engine at operating temperature. Where quietness is desired and vehicle is not operated at high speed or on heavy hauling, etc., exhaust valves may be adjusted to .015" minimum.

CARBURETER ADJUSTMENTS
Increased resistance on foot throttle indicates a clogged pump jet. Pump jet should be removed and cleaned with compressed air, which, in many cases, will remove the dirt or lint. However, it is usually advisable to replace the pump jet, as its cost is nominal. All jets and ball checks must be seated gasoline-tight.

Poor acceleration may be due to damaged or worn plunger leather in accelerating pump, corrosion in pump cylinder, loose or cracked cylinder, cracked plunger cup or bent pump arm (parts which may be replaced at small cost). If plunger is removed from cylinder, always use loading tool in re-assembling to avoid damage to plunger leather.
Holes in pump arm provide pump adjustment. Set to longest stroke for extreme cold weather, shortest stroke for hot weather driving.

Copyright 1938
Spark Plug Gap .040"
Set
Breaker Points
.018"
Use Neon Timing
Light or Timing Light
Breaker Points to
open 5° before
top dead center
Motor Tune-Up—Be Accuratel Always Use Feeler Gauges(
CAUTION: Change worn or leaky flange gaskets. Tighten manifold bolts and test compression before adjusting carbureter.
Set Valves Hot (Road Operating Temperature) Intake .010" Exhaust .020"
Idle Adjustment
Screw Setting
I to 2
Turns Open
If carbureter loads up after considerable service, float level should be checked. Wear on lip of float lever will'raise float level. Float level may be reset by bending lip of float lever down to raise float level or bending lever up to lower float level. Only a very slight bend is needed.
If motor stalls while idling, reset idle adjustment screw and throttle lever adjusting screw. If these adjustments do not correct the trouble, remove low speed jet tube and clean thoroughly with compressed air. Examine and see that tube seats gasoline-tight in body casting, top and bottom. If not, replace with a new tube of identical specifications. NEVER CHANGE A LOW SPEED JET TUBE FROM ONE CARBURETER TO ANOTHER.