Buick LeSabre 1965 Service Manual page 107

ENGINE FUEL A N D EXHAUST SYSTEMS
2-BARREL ROCHESTER 3 - 3 1
SECTION 3-E
ROCHESTER 2-BARREL CARBURETOR
CONTENTS OF SECTION 3-E
Paragraph
Subject Page Paragraph
Subject
Page
3-14 Description and Operation of
Rochester 2-Barrel Carburetor
3-15 Disassembly, Cleaning and
Inspection of Rochester
2-Barrel Carburetor
3-16 Assembly of Rochester
3-31 2-Barrel Carburetor
3-17 External Adjustment of
Rochester 2-Barrel
3-35 Carburetor
3-36
3-38
3 - 1 4 DESCRIPTION AND
OPERATION OF
ROCHESTER 2 -
BARREL CARBURETOR
a. General Description
The Rochester Model 2GC carbu-
retor is of the side bowl design.
While not interchangeable, the
carburetors used on automatic
and standard transmission cars
are basically the same, and the
description and service opera-
tions are identical. The only dif-
ference is in some of the internal
calibrations. The carburetor float
bowl is located forward of the
main bores of the carburetor.
BOWL -
VENT
IDLE
MIXTURE
NEEDLES
_ CHOKE HOUSING
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C
HOKE
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Figure 3-25—Rochester 2GC Carburetor
Assembly - 300 Engine
The carburetor is compact in de-
sign in that all of the fuel meter-
ing is c e n t r a l l y located. See
Figure 3-25.
This carburetor uses a calibrated
cluster design, which places in a
removable assembly, the main
well tubes, idle tubes, mixture
passages, air bleeds and pump
jets. This cluster can easily be
removed for cleaning and inspec-
tion purposes. The cluster fits
on a flat portion of the carburetor
bowl in front of the main venturi
with a gasket underneath. See
Figure 3-26. The idle and main
well tubes are permanently in-
stalled in the cluster body by
means of a precision pressed fit
and, therefore, cannot be serv-
iced separately. The main noz-
zles and idle tubes are suspended
in the fuel in the main wells of
the float bowl.
The main metering jets are of the
fixed type. Metering calibration
is accomplished through a system
of calibrated air bleeds which
give the correct air/fuel mixtures
throughout all operational ranges.
The Rochester Model 2GC carbu-
retor employs the use of a vac-
uum operated power system for
extra power when needed. Power
mixtures are regulated by drop
in engine manifold vacuum re-
gardless of the degree of throttle
opening. Thereby, additional fuel
can be supplied for power mix-
tures according to the engine
demands.
Figure 3-26—Main Body Parts
The pump system has a vented
type pump plunger. This is ac-
complished by means of a vapor
vent ball in the pump plunger
head. By v e n t i n g the pump
plunger, any fuel vapors which
form in the pump well are vented
to the fuel bowl during "hot"
engine operation. This insures
that the pump well and passages
will be primed with solid fuel at
all times, thereby improving ac-
celerator pump action.
The carburetor is i n t e r n a l l y
vented through a hole in the air
horn and is externally vented
through a capped vent hole lo-
cated in the center of the carbu-
retor air horn just above the float
bowl.
Adjustments have been made as
simple as possible. They consist
of idle, float level, float drop,