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10-68
GROUP 10- FUEL SYSTEM
EJ
HOT AND COLD TYPE AIR INTAKE SYSTEM -
VACUUM OPERA TED
DESCRIPTION AND OPERATION
DESCRIPTION
The air cleaners as fitted to the
351C-2V and 351C-4V engines are
basically the same design, with the
filter elements being interchangeable.
The air cleaners feature
inlet
mani-
fold vacuum operated, bi-metallic
switch controlled
(Fig.
1), hot and
cold type duct and
valve
assembly.
The duct and valve assembly in-
corporates an access to the under-
hood area
(cold),
similar to the con-
ventional type air filter, and has in
addition an access connected by
means of a flexible pipe to the front
of the exhaust manifold housing
(hot).
OPERATION
From initial cold engine start, high
inlet manifold vacuum/air pressure
difference overcomes the duct butter-
fly spring tension and closes the duct
cold access opening and opens the
hot access (from exhaust manifold)
opening, as shown in Fig. 2 (A). As
the engine warms, the resi.Iltani hot
air flowing through the air cleaner
causes the thermal-operated bi-metal
switch (Fig. 1) to unseat the bleed
valve which 'bleeds' vacuum from
the duct valve. The reduced vacuum/
air pressure difference is overcome
by the spring in the duct valve which
pens the cold access (under hood)
and closes the
hot access (Fig.
2
(B)).
Incoming air is filtered through
the filtering element as with the
conventional dry type air cleaner.
TO
VACUUM SOURCE TO DUCT
VALVE
MOTOR
V1231-A
FIG.
1.- Bi-
Metal Switch
DUCT AND VALVE
ASSEMBLY TEST
The vacuum-operated duct valve
is used on all 351 C engines.
1. The duct valve should be open
when the engine is off.
2. Start the engine. The valve
should close during engine idle unless
the engine has reached normal operat-
ing temperature. If the engine is cold
and the valve does not close during
idle, check for disconnected vacuum
lines to the vacuum motor and bi-
metal switch. Check the bi-metal
switch to see that the bleed valve is
seated.
3. Open and close the throttle
rapidly. The valve should open dur-
ing throttle opening. If the valve does
not function properly, check for a
binding condition at the valve.
Correct as required.
4. The bi-metal switch can
be
functionally checked by subjecting
the switch to heated air or removing
and immersing the switch in water
heated to 105-110 degrees F. Only
slight movement of the bi-metal is
necessary to unseat the bleed valve.
VACUUM OFF
VACUUM ON
FIG. 2- Duct and Valve Assembly
HOT AND COLD TYPE VACUUM
OPERA TED AIR CLEANER
Removal and Installation
Refer to Group 19 for the air
cleaner assembly recommended
maintenance mileage
interval.
REMOVAL
1. Remove the wing bolt or nut
retaining the air cleaner and duct to
the carburettor and remove cover.
2. Disconnect the crankcase venti-
lation system hose and loosen the
clamp that secures the exhaust
shroud hose to the air cleaner duct.
3. Raise the air cleaner and duct
assembly and disconnect the vacuum
source hose at the bi-metal control
valve (inlet manifold side only).
4. Remove the
air
cleaner and
duct assembly from the carburettor:
To prevent dirt from entering the
carburettor, the filter element must
never be removed when the air
cleaner body is mounted on the
carburettor.
5. Remove the air cleaner cover
and filter element. Discard the air
cleaner mounting gasket if it is exten-
sively worn or damaged. On the ram
air system, inspect the hood-to-air
cleaner seal for all-around contact.
Replace the gasket or seal if it is
worn or damaged.
CLEANING AND INSPECTION
Refer
to
Pagel0-13,
for
the car-
buretor air cleaner and filter element
cleaning and inspection procedure.
INSTALLATION
1. Install a new air cleaner to car-
burettor mounting gasket, if required.
On all351
C.I.D.
carburettor applica-
tions, torque the air cleaner
mounting stud to specification.
2. Position the air cleaner and air
intake duct and valve assembly on the
carburettor and shroud tube.
3. Connect the vacuum source
hose at the bi-metal control valve.
Secure the clamp attaching the
shroud to the air duct.
4. Install a new filter element in
the air cleaner body, if required. If
the word TOP is indicated on
the filter element, make sure the
word TOP faces upward. Make
sure the filter element is pro-
perly seated. Install the air cleaner
cover and retaining wing nut
HOT AND COLD AIR INTAKE
DUCT AND VALVE ASSEMBLY
REMOVAL
1. Remove the retaining cap screws
that secure the air intake duet and
valve assembly to the air cleaner.
2. Remove the air intake duct and
valve assembly from the engine.
INSTALLATION
1. Install the air intake duct and
valve assembly on the exhaust mani-
fold shroud tube.
2. Connect the air inlet duct and
valve assembly to the air cleaner and
tighten the retaining cap screws.
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