Classic cars repair

Old Carburetors

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b) Idling throttle screw: Screw the idling throttle screw (Z) (Fig. 1) into its shoulder and then back it out from 1 1/4 to 1 3/4 turns.
c) Main needle: Loosen the cap screw (V) which clamps the lever to the main needle (T). Turn the main needle to the left until it seats and then turn it to the right from 5/8 to 3/4 of a turn.
d) High-speed needle: Loosen the lock nut (R) on the high speed needle (Q) (Fig. IA.) Turn the needle carefully into its seat with the fingers and then unscrew it % to IA of a turn. hold the needle with screw driver and then lock the nut.
Fig. 3. Side view of Pierce Arrow carburetor for Series 32 and 33 car. The tube (Se) connects with the high speed nozzle (Q (frig. IA) and supplies it with gasoline. The screw (He) is provided to hold venturi in place.3. Final Adjustments
Start the engine by priming and allow it to run until it is warm. The spark lever should be advanced % of its travel.
Increase the engine speed until it is equivalent to 20-30 miles per hour in high gear. If necessary, further adjust the main needle (T) until the engine runs at the highest number of revolutions per minute without a change in throttle lever setting.
Loosen screw (W) which clamps the main needle regulating wire. Set the arrow on the dash regulator (a carburetor regulator on dash connects with W) in a vertical position and set the main needle adjusting lever at right angles with the engine. Now tighten screw (W) and cap screw (V). This setting will permit a richer or leaner adjustment on the main needle by means of the dash control.
Now drive the car on the road. It should not travel slower than 3 to )i miles per hour in high gear. Keep the idling screw (Z) closed as much as possible.
If the adjustment is satisfactory at thirty miles per hour with the dash regulator in the neutral position, the main needle setting may be considered right.
If at fifty miles per hour the car operates better with the dash regulator toward either lean or heavy, the high speed needle adjustment should be cut down or increased respectively. (Screwing in will give less gasoline and screwing out more.)
If the carburetor is correctly adjusted, the car can be run through the entire range of speeds without having carburetor "load up" or have a "hollow spot." If economical operating is desired, the dash regulator should be kept on the lean side, after engine is warm.
Gasoline system: The gasoline supply is carried in a tank mounted on the rear of the car. From this tank the gasoline is drawn by suction to a vacuum tank located on dash under engine hood. Gasoline flows from vacuum tank to carburetor by gravity.
A primer (not shown) is mounted in inlet pipe of engine. It is operated by pulling out on a handle located on left side of dash. Pulling out on handle opens needle valve which is held on its seat by spring pressure and permits gasoline drawn from carburetor feed pipe to be injected into inlet pipe. The purpose of the primer is to facilitate starting engine when cold.
The adjustments on the carburetor are as follows:
First, idling adjustment: Turn adjusting screw (Z) into shoulder and then back off from % to 1½ turns.
Main adjustment: This adjustment is made by turning needle (T) to the left into its seat and then backing off from liy to a) turns. Before making this adjustment, loosen clamping bolt on lever (W) which is connected with dash regulator.
After adjustment is obtained tighten clamping bolts on this lever with dash regulator control set in center position.
Occasionally, the gauge strainer plug (C) (Fig. 4) at bottom of carburetor float chamber should be removed and cleaned. The idling jet (IJ) (Fig. 5) can be removed and blown out if stopped up.
The throttle valve (E) which is of the butterfly type is located above venturi tube. It is controlled by right-hand lever on steering column and by accelerator pedal.
An adjustable stop screw (P) in throttle lever holds valve slightly open when engine is running at its lowest speed.
Accelerating well: To provide smooth and powerful acceleration under all conditions, an accelerating well is built into carburetor, as shown in Fig. 5. The action of this is entirely automatic, it being controlled by opening the throttle, which operates a plunger rod on stem (St).
Reed valves: Air necessary to form an explosive mixture in combustion chamber of engine is admitted to carburetor through openings in plate (PL) covered by flat steel springs or reeds 1, 2 (light and heavy) which is located between mixing chamber and air admission housing. The tension on springs and the opening given them after being set by the manufacturer, should not be altered. The setting is as on the 33. The total travel is controlled by spring (G) (Fig. 7).
Inlet manifold heat regulator: To provide the most efficient carburetion, heat from the exhaust is conducted through a chamber around inlet pipe to heat the mixture.
The valve (not shown) which regulates the amount of heat admitted should he set in center position for all ordinary temperatures. In extremely hot wear her move valve lever into "off" position. In extremely cold weather prove into "on" position.
Carburetor regulator: The regulator on the dash connects with (W) (Fig. 5) and gives a rich or lean mixture to the carburetor. Use the rich mixture for starting and lean when driving after engine has warmed up.
Fig. 4. Side sectional view of Pierce-Arrow carburetor for series 80 car. Fig. 5. End sectional view showing idling jet and accelerator plunger and its connection with throttle lever. Figs. 6, 7. Section showing auxiliary air reed.

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Carburetor Manuals: Pierce Arrow