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Form 6449B—Canadian
BUICK 474$
June, 1940
Reprinted June, 1946

BUICK EIGHT MODEL 40 & 50 1940

Casting No. 311 on Face of Flange
Dual Down-Draft Climatic Control Carbureter—Model 474S—List Price $44.10
A $10.00 exchange allowance is deducted from the list price if buyer turns in old carbureter.
CARBURETER SPECIFICATIONS
For Buick 8 Cylinder Engine: 3-3/32 Inch Bore, 41/8 Inch Stroke
Dimensions: Flange size, I inch dual, 3 bolt type. 7 m.p.h. on level road.
Primary venturi, 11/32 inch I. D.
Secondary venturi, 21/32 inch I. D.
Main venturi, I-I/16 inch I. D.
Float Level: Distance from float to bowl cover, when needle is seated, to be 3/16 inch. (Use gauge No. T109-28.)
Vents: Outside, No. 10 drill—four holes. Inside, none.
Anti-percolation Vent Tube: Above nozzle, 20° tip. Inside diameter, No. 42 drill. Relation tip of tube to inside primary venturi, .065 inch.
Gasoline Intake: Square vertical needle. Size, No. 42 drill
hole in needle seat.
Gas Line Connection: 5/16 inch fitting.
Low Speed Jet Tube: Jet size, No. 70 drill.
By-pass (plug), size No. 55 drill.
Economizer in body, size No. 58 drill.
Idle bleed, size No. 56 drill.
Idle Ports: Upper port, slot type, length, .100 inch; width, .030 inch.
Idle Port Opening: .060 to .066 inch above upper edge of valve with valve closed tight.
Lower Port (For Idle Adjustment Screw): Size .0615 to .0655 inch diameter.
Set Idle Adjustment Screw: i/2 to li/4 turns open. For richer mixture turn screw out. Do not attempt to idle engine below
Motor Tune-Up--Be Accurate! Always Use Feeler Gauges!
CAUTION: Change worn or leaky flange gaskets. Tighten manifold bolts and test compression before adjusting carburetor.
Use Timing Light
Breaker Points to
Open 4°
before T. D. C.
MOTOR SERIAL NUMBERS
3976130 to 3984999
3990175 and higher
Main Nozzle: In primary venturi, angle 45°. Closed tip. In-side diameter No. 30 drill. Upper hole: No. 75 drill on 45° angle. Lower hole: No. 52 drill on 60° angle.
Metering Rod (Vacumeter Type): Economy step, .0635 inch diameter. Second step tapers to .0595 inch diameter. Third step, .0595 inch diameter. Power step, .056 inch diameter. Length of rod 2-59/64 inches.
Metering Rod Jet: 082 inch diameter.
Metering Rod Setting: Use gauge, part No. T109-I 13 (2.280 inches).
Accelerating Pump: High pressure type (spring operated lever) with adjustable stroke.
Discharge jet, size No. 74 drill.
Intake ball check, size No. 40 drill.
Discharge ball check, size No. 50 drill.
Relief passage to outside, No. 42 drill.
Pump Adjustment: 21/64 inch plunger travel (full throttle position) medium stroke. Use gauge T109-117S.
Choke: Carter Climatic Control, set I point lean. Butterfly type, offset valve.
Choke Heat Suction Hole, in body, size No. 40 (.098") drill. Vacuum Spark Port: .039 to .041 inch diameter. Bottom of port .052 to .056 inch above valve.
Spark Plug Gap .025"
Set
Breaker Points
.015"
Set Valves Intake .015" Exhaust .015"
Idle Adjustment
Screw Setting
i/7 to 11/4
Turns Open
Correct Float Level
(Remove Cork Gasket)
3/16 Inch
BRIEF CARBURETER
PUMP ADJUSTMENT: With pump connector link in medium stroke and throttle adjustment screw backed out, pump plunger should travel 21/64" from closed to wide open position. Adjustment can be made by bending throttle connector rod at lower angle. (Use tool T109-75.) Pump travel can be measured by placing gauge T109-117S on rim of bowl around plunger shaft and measuring from top surface of connector link at pump shaft.
METERING ROD ADJUSTMENT: Should be made when reassembling carbureter or when leaner than standard rods are installed. (Do not disturb pump adjustment.) Correct setting of metering rods is important. Procedure is as follows:
A. Back out throttle lever adjusting screw so that throttle valves seat.
B. Insert metering rod pin in vacuum piston shaft.
C. Insert one metering rod gauge No. T109-113 in meter-
ing rod hole in place of metering rod. Make sure that
gauge seats in metering rod jet.
D. Depress vacuum piston shaft lightly until contact is made with tongue on metering rod arm. There should now be less than .005 inch clearance between metering
Copyright 1940
by Carter Carburetor Corporation
All rights reserveo.
ADJUSTMENTS
rod pin and shoulder of notch in gauge.
E. Adjustment can be made by bending tongue on anti-percolator arm, using tool T109-105.
F. Remove gauge and replace metering rods, metering rod disks and metering rod spring on pin. Then insert pin spring in groove on pin, and hook metering rod spring on metering rods.
STARTER SWITCH: Adjustment should be made with Carter tool No. T109-155S, obtainable from your Carter distributor with complete instructions.
Note: When connecting switch wires, attach red wire to switch terminal closest to motor.
UNLOADER ADJUSTMENT. With throttle wide open, distance between upper edge of choke valve and inner wall of air horn should be 3/16". (Use gauge T109-2S.) Adjustment can be made by bending lip on fast idle connector link. With throttle wide open, push choker valve open. Choke should lock in wide open position. If it does not lock, re-check unloader adjustment. Closing the throttle will release choker valve. Choker trip lever Is notched out for this setting.
FAST IDLE ADJUSTMENT: Hold choker valve tightly