Ford COUGAR 1968 Shop Manual page 536

GROUP 10
-
Fuel
System
IDLE FUEL RESTRICTION
/
+
IDLE A ~ J U S T I N G IDLE FUEL
IDLE
TRANSFER
SLOT
NEEDLE
DISCHARGE PASSAGE
A I R IDLE
\
TRANSFER PASSAGE
82251.8
FIG.
6-Typical
Holley 4-V Idle Transfer System
FIG.
7-Typical
Holley 4-V Accelerating System
fuel systems (Fig. 5) for each pri-
mary venturi and identical idle fuel
systems for each secondary venturi.
Idle fuel is discharged into both the
primary and secondary venturis. Idle
fuel for the primary venturis is drawn
from the primary fuel bowl, and idle
fuel for the secondary venturis is
drawn from the secondary fuel bowl.
Fuel flows from the primary fuel
bowl through the main jets into a
smaller angular passage (idle feed)
that leads across to the idle well.
Fuel flows from the secondary
fuel bowl through the main metering
restrictions of the rear metering body
and into the idle well. The fuel flows
up the idle well, where it is mixed
with air from the idle air bleeds.
P R I M A R Y S T A G E
After leaving the idle well, the
fuel-air mixture flows through a short
horizontal passage and then down an-
other vertical passage. At the bottom
of this vertical passage, the fuel-air
mixture branches in two directions,
one through the idle discharge pas-
sage and the other to the idle trans-
fer passage (Fig. 6).
The fuel in the idle discharge pas-
sage flows past the idle adjusting
needle which controls the fuel dis-
charge a t idle. From the idle adiust-
ing needle chamber, the fuel goes
through a' short passage in the main
body and down another passage into
the throttle body. An internal needle
type limiter, located in the idle chan-
nel of the throttle body, controls the
maximum idle fuel richness.
The
limiters are installed and sealed dur-
ing manufacture, and no attempt
should be made to adjust the setting.
During off-idle operation when the
throttle plate is .moved slightly, the
fuel flows through the idle transfer
passage. (Fig. 6) in the metering body
and then into the main body through a
restriction. From the main body, it
flows into a passage i n the throttle
body. As the idle transfer slot is ex-
posed to manifold vacuum, fuel is
discharged.
As the throttle plate is opened
still wider and engine speed increases,
the air flow through the carburetor is
also increased. This creates a vacuum
in the booster venturi great enough to
bring the main fuel system into oper-
ation. The flow from the primary
stage idle fuel system begins tapering
off as the main fuel system begins
6 1 4 0 5 - 6
discharging fuel.
S E C O N D A R Y S T A G E
After leaving the idle well or idle