Chevrolet with Old Carter Carburetors : CHEVROLET PASSENGER & TRUCK G. M. C. TRUCK 1939 1940 1941 1942

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CHEVROLET PASSENGER & TRUCK G. M. C. TRUCK 1939 1940 1941 1942

Form 6466C—Canadian CHEVROLET & G.M.C. TRUCK 420$
January, 1941
Reprinted August 1945
CAR SERIAL NUMBERS
Chevrolet Passenger—Series 1000, 1200
1941—Oshawa 11—00001 and higher
1941—Regina 11—80001 and higher
1942—Oshawa 21—00001 and higher
Chevrolet Truck
Series 1300, 1400, 1500, 1600
1941—Oshawa 11—05001 and higher
194I—Regina 11—80001 and higher
1942—Oshawa 21—00001 and higher
G.M.C. Truck
1941 Series 9300, 9400, 9500, 9600
I941—Serial No. 19—00001 and higher
1942—Serial No. 29—00001 and higher
Casting No. 365 on face of flange.
W- l DOWN-DRAFT CARBURETER No. 420S—LIST PRICE $ 17.65
A $2.50 exchange allowance is deducted from the list price if buyer turns in old carbureter.
CARBURETER SPECIFICATIONS


CHEVROLET PASSENGER & TRUCK G. M. C. TRUCK 1939 1940 1941 1942


(Not used on cab-over engine models)
For Chevrolet Six Cylinder Engine:
Dimensions: Flange size, II/4 inch S. A. E. Primary venturi, 11/32 inch I. D.
Secondary venturi, 11/16 inch I. D. Main venturi, 11/4 inch I. D.
Float Level: Distance from float (at free end) to float chamber cover to be 1/2 inch plus or minus 1/64 inch when needle is seated. (See cut.)
Vents: Outside, none. Inside (balance vents) above choke valve through shaft, size No. 27 drill. Below choke valve, 3/16 inch drill.
Gasoline Intake: Square vertical needle. No. 48 drill size in needle seat.
Gasoline Line Connection: Compression type nipple, 5/ 16 inch.
Low Speed Jet Tube:
Jet size, No. 70 drill.
By-pass in body, size No. 56 drill.
Economizer jet; size .062 to .063 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: Top of lower port .041 to .045 inch above top edge of valve, with valve closed tight.
3½ Inch Bore, 334 Inch Stroke
Idle Screw Seat: Size No. 52 drill.
Idle Adjustment Screw: Set I to 2 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, .0675 inch diameter; second step tapers to .057 inch diameter; third step tapers to .050 inch diameter; power step, .040 inch diameter. Length, 3% inches.
Metering Rod Jet: Size, .095 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—Offset, butterfly type.
Throttle Valve: (1939) Opens to within 3° to 6° from perpendicular. (1940) Opens to within 0° to 3° from perpendicular.
Vacuum Spark Port: Slot type: size, .040 by .125 inch. Bottom
of port .000 to .004 inch above top of valve.
Motor Tune-Up—Be Accurate! Always Use Feeler Gauges!
CAUTION: Change worn or leaky flange gaskets. Tighten manifold bolts and test compression before adjusting carbureter.
Spark Plug Gap .040"
CARBURETER ADJUSTMENTS
Use Neon Timing
Light or Timing Light
Breaker Points to Exh. open 50 before top
dead center Exh.
Set Valves—Hot
Int. .006"-.008" .013"-.015" (Pass. Cars) .018"-.020" (Trucks)
Set
Breaker Points
.018"
Correct Float Level
(Remove Cork Gasket
and measure from
machined surface of
float cover)
!/2 Inch
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 evel. 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 CAR-B URETER TO ANOTHER.
Copyright 1941