Float Adjustment; Accelerator Pump Piston Stroke Adjustment; Idle Speed Adjustment - Ford LRG-423 Service Manual

03-36
Auxiliary Systems
03-36
HOLLEY ONE-BARREL CARBURETOR MODEL 1940 (Continued)
As the throttle lever is moved, the pump link, operating
through a series of levers and a drive spring, pushes
the pump cylinder down, seating the pump cup against
the stem face. Fuel is forced through a passage
around the pump discharge jet which is drilled in the
main body.
When the pump is not in operation, vapors or bubbles
forming in the pump cylinder can escape through the
stem clearance hole of the floating piston cup and flow
past the pump stem.
PUMP
OPERATING
ROD
PUMP DRIVE
SPRING
/
PUMP/
LINK
/
/
CHECK BALL
WEIGHT
PUMP
PISTON AND
STEM ASSEMBLY
PPD0020
Adjustments
There are four adjustable items on the Holley Model
1940. They are idle speed, idle mixture, accelerator
pump piston stroke and float adjustment. The entire
carburetor assembly is to be removed from the intake
manifold to perform a float level adjustment. The pump
piston stroke adjustment is made by expanding or
contracting a " U" adjustment bend in the accelerator
pump linkage. Idle speed adjustment is performed by
turning the idle speed screw with the engine at normal
operating temperature. Idle mixture adjustment is
performed by turning the idle mixture screw with the
engine at normal operating temperature.
Float Adjustment
To perform the float adjustment, the entire carburetor
assembly must be removed from the intake manifold
and all connections to the carburetor disconnected.
Remove the fuel bowl cover from the carburetor main
body assembly and drain the fuel from the fuel bowl.
Invert the carburetor assembly. Place a straightedge
across the surface of the fuel bowl. The toes of the
floats (the portion of the float that hangs farthest from
the fuel inlet) should just lightly touch the straightedge.
To adjust, bend the float tang (lever). Both floats must
be parallel to the straightedge and not cocked or offset.
Bend the float shafts to even out the floats. Recheck
float level.
CAUTION: When bending the tang, do not force the
Viton-tipped fuel inlet needle against the seat or
theviton tip on the needle will be damaged.
FLOAT ADJUSTMENT
STRAIGHT EDGE
FLOAT ASSEMBLY
PPD0021
Accelerator Pump Piston Stroke Adjustment
The accelerating pump stroke is controlled by the
position of the accelerating pump link in one of the
three slots of the rocker arm. Use the middle slot for
the LRG-423 application.
Idle Speed Adjustment
Idle speed adjustment is performed with the engine air
cleaner in place. The engine must be run at fast idle
for 5-I 0 minutes or until normal operating temperature
is reached. The idle speed screw is found in the
throttle body. The tip of the screw rests on a tang on
the outer throttle shaft assembly to control engine idle
speed. Make sure the screw is in contact with this tang
when setting engine idle speed. Connect a tachometer