Figure 4-52. Vacuum Progressive Linkage Operation.
g. Four-Barrel Carburetor (Fig. 4-54). The four-
in the throat is downward, upward, or sideways,
barrel or four-venturi carburetor consists of two primary
venturis on a fixed throttle shaft that are progressively
linked to two secondary venturis that are also on a fixed
422. Primer System (Fig. 4-56). Some gasoline
throttle shaft. The four- barrel carburetor is popular for
engines are fitted with a primer system to aid cold
the V-8 engine configurations for the following reasons:
starting. The primer system consists of a hand pump
that forces gasoline through a line to inject it at strategic
(1) The intake manifold may be divided to
locations along the intake manifold. The system is not
separate consecutive cylinders (para 4-20c).
used very much in modern equipment.
(2) The carburetor better serves the engine
4-23. Degasser System (Fig. 4-57). The degasser
throughout the entire load and speed range.
system Is designed to shut off the supply of fuel to the
idle circuit whenever there is high manifold vacuum such
4-21. Updraft, Downdraft, and Sidedraft Carbu-
as periods of deceleration preventing large amounts of
retion. Carburetors may be built so that the airflow
fuel from being drawn into the engine through the idle
port. The degasser consists of a needle valve, a spring
that holds the needle valve open, and a