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of the carburetor, controls the throttle
plates in
the usual manner. When governing
speed is
reached, a combination of venturi
and manifold
vacuum acts on the governor diaphragm
to close
the throttle plates. Two calibrated
by-pass jets
in the vacuum passages meter the
vacuum from
the venturi and the manifold to
provide the correct
balance for proper operation of
the governor. At
speeds below governing rpm, this
vacuum is
weakened by air bleeding through
the governor
valve so that no premature governing
action will
occur. Filtered air from the carburetor
air
cleaner enters the governor system
through the
governor vent tube. The air flows
through an air
line to the housing enclosing the
governor rotor.
A combination of low pressure from
the venturi
and manifold transmitted through
the governor
system passages, draws the air past
the governor
valve and through another air line
to the throttle
actuating unit on the carburetor.
In the controlling
unit, centrifugal force acting on
the rotor, which
has kept pace with engine speed,
overcomes the
tension of the valve spring and
tends to close the
governor valve when governing speed
is reached.
This greatly restricts the amount
of air bleeding
through to the diaphragm on the
carburetor, thus
allowing the combined venturi and
manifold pres
sure differential to operate the
diaphragm.
As the pressure differential across
the dia
phragm increases, the diaphragm
moves the
governor lever against the tension
of the governor
spring to close the throttle plates.
The governed
engine speed is held for constant
load by centri
fugal force on the valve balanced
against the tension
of the valve spring. Any slight
change in engine
speed due to load restriction will
cause the gov
ernor valve to react immediately,
either increas
ing or decreasing the amount of
air bleeding
through the governor valve orifice.
A change in
the amount of air bleed will, in
turn, cause an
instant response from the diaphragm
to increase
or decrease the throttle plate opening.
When the
accelerator is released, control
is taken from the
governor by the external throttle
lever and the
return spring in the accelerator
pedal linkage
closes the throttle plates to bring
the engine to
any desired lower speed.
Although the entire governor system
is de
scribed, only the throttle actuating
mechanism
on the carburetor is included in
theoverhaulpro
cedure presented in this manual.
This portion of
the governor can be cleaned and
serviced readily,
also the governor rotor can be
serviced independly.
See Holley Manual B-183 for servicing
of governor
control valve.
OVERHAUL
1. INTRODUCTION
The approved method for properly
overhauling
a carburetor calls for the complete
disassembling.
A thorough cleaning and a careful
inspection of
each part is essential. Defective
parts should
be replaced with genuine Holley
replacement parts
and the carburetor should be carefully
rebuilt.
Care in rebuilding and accuracy
in adjusting the
carburetor will insure the same
top quality per
formance engineered into every
Holley Carburetor.
2. SPECIAL TOOLS
3.
MASTER REPAIR KITS
The overhaul procedure which follows
can be
accomplished with ordinary tools
if a reasonable
amount of care is exercised.
However, factory
approved tools are recommended
to facilitate
overhaul and to prevent damaging
of vital parts.
The special tools recommended for
use in
the overhaul of these carburetors
are listed above:
Master Repair Kits contain Holley
replace
ments for parts which are subject
to wear or may
be damaged in disassembly. The
disassembly
procedure includes instructions
to discard all
gasket and parts which have replacements
in the
Master Repair Kits. The proper
kit for each
carburetor is listed in the current
Holley Carbu
retor Parts Catalog.
