Classic cars repair

Old Carburetors

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('I'3— Standard Six T4 — Master Six) The Marvel model "T" carburetors are of the automatic air-valve, two jet, heat-controlled types.
The construction embodies a main body or mixing chamber (1, lig. 1), and a conventional float chamber bowl (2), with fuel strainer (3) attached at point of entrance of fuel to bowl.
Within the mixing chamber are two nozzles which proportion the amount of gasoline used in the mixture.
Fig. 1. Sectional side view of the model "T" Marvel carburetor.
Fig. 2. Sectional end view.
One of these nozzles (' ), called the "low speed," is regulated by the gasoline adjustment needle (5) at bottom of carburetor and the other (6), called the "high speed," is controlled by the automatic air valve (7).
An air screw (8) is provided which regulates the pressure of the air-valve spring (9) enclosed therein.
Within this screw is also enclosed a plunger (10), connected by a link to the air valve (7).
The function of this plunger is to provide a resistance in addition to that of the air valve spring to assist in acceleration. This arrangement of plunger (10) and air valve screw (8) is termed the dash pot.
A further control of the high-speed jet (6) is provided by the fuel-metering valve (11, Fig. 2) operated by the carburetor throttle (12, Fig. 2) through link (13).
This valve provides the maximum fuel feed to the "high-speed" nozzle (6) when the throttle is fully opened for high speeds and for quick "pick up."
1 An air cleaner of the AC make is placed on the main air intake (Fig. 3) of carburetor on the Buick, Nash, and Oakland. The Buick and Nash carburetors are identical so far as adjusting is concerned, the only ,change being in casting shape, calibration, and levers.

The Oakland 1926 model Marvel A-2S carburetor is greatly different. See page 1275.
During the ordinary driving ranges this valve (11) controls the amount of fuel being used, thus providing all the economy possible. 'i his valve is entirely automatic and requires no adjustment.
A choke button (see top button above J, in Fig. 3, is provided on the instrument board to assist in starting. It is connected to (15, Figs. 1 and 2).
Pulling out this button closes a butterfly valve (14, Fig. 2) the air intake passage of carburetor, which restricts the air opening of the carburetor, and consequently produces a richer mixture. This button should be released at once upon starting.
A control lever (J), (see Fig. 3) is also placed on the instrument board to provide for manual regulation of heat control in addition to the automatic heat control mechanism of the carburetor.
Heat Control
The carburetor and manifolds have been designed to utilize the exhaust gases of the engine to insure complete vaporization and a consequent minimum consumption of fuel.
Fig. 2A. This illustration gives the reader an idea how the main exhaust can be directed down through the riser and out the tube by damper control valve (L) and another valve in tube (M) explained in text.
This is accomplished by the use of a double-walled riser which carries the throttle placed between the carburetor and the intake manifold.
This riser is connected to the exhaust manifold in such a manner that the exhaust gases pass between the walls (W) (Fig. 2) of the riser, and through the outlet tube (M) (Fig. 1) front riser to the exhaust pipe.
The amount of heat thus furnished to the riser jacket is controlled by two valves: one in the exhaust pipe above the outlet tube from riser and one in the outlet of riser heat jacket.
The valve (A) (Fig. 3), in the exhaust pipe is connected to the throttle lever of carburetor in such a manner that the greatest amount of heat is had iu the jackets (W) (Fig. 2) of riser when the throttle (12) is only partly open, as in idling and at slow speeds, and a decreasing amount as the throttle is opened further for higher speeds.
By means of the heat-control lever (J) (Fig. 3) on instrument board this automatic action of the heat valve may be varied to suit weather and driving conditions.
The valve (A), (Fig. 3) described above in main exhaust line at front end of engine, has a shaft which has a slot in the end. This slot indicates position of

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Carburetor Manuals: Marvel