Exhaust Emission Control Systems - Ford COUGAR 1968 Shop Manual

PART 8-3
-
289 And 302 V-8 8-63
cover. The air then enters a spring-
loaded regulator valve that regulates
the amount of air to meet changing
operating conditions. The air is then
directed to the intake manifold
through the crankcase vent hose.
At idle speed, intake manifold vac-
uum is high. The high vacuum over-
comes the tension of the spring pres-
sure and moves the valve to the
Low-Speed Operation position (Fig.
13). With the valve in this position,the
ventilating air passes between the
valve (jiggle pin) and the outlet port.
With the valve in this position, there
is minimum ventilation.
As engine speed increases and man-
ifold vacuum decreases, the spring
forces the valve to the full open posi-
tion (Fig. 13). This increases the flow
of ventilating air.
TO
INTAKE
NIFOLD
LOW SPEED OPERATION-
HIGH MANIFOLD VACUUM
HIGH SPEED OPERATION-
LOW MANIFOLD VACUUM
I
FIG.
73-Crankcase Ventilation
Regulator Valve O p e r a t i o n
EXHAUST EMISSION
CONTROL SYSTEMS
All 1968 engines incorporate ex-
haust emission control systems namely
Imco on most automatic transmission
vehicles and Thermactor on all others.
Both the I M C O and Thermactor ex-
huast emission control systems are
designed to reduce the hydrocarbon
and carbon monoxide content of gaso-
line engine exhaust gases. By con-
trolling the amount of contaminants
emitted through the exhaust system
to an acceptable minimum, air pollu-
tion is reduced.
IMCO
The I M C O exhaust emission control
system controls engine combustion at
a level to reduce contaminants nor-
mally emitted through the exhaust
system. This is achieved by using a
specially-calibrated carburetor and
distributor.
THERMACTOR
by the Thermactor system is achieved
exhaust ports of the cylinder heads.
by burning the hydrocarbon and car-
To accomplish this burning of the
bon monoxide concentrations in the contaminants, air under pressure is
BYPASS TIMING ORIFICE
DIAPHRAGM CHECK VALVE
DIAPHRAGM RETURN
INTAKE MANIFOLD VACUUM
TO AIR MANIFOLD
LVE
AIR PASSAGE
TOATMOSPHERE
BYPASS AIR SHUT-
OFF VALVE PLATE
(NORMAL POSITION)
7
FROM AIR PUMP
AIR BYPASS AND PRESSURE
RELIEF VALVE PLATE
I I
4
AIR SILENCING CHAMBER
FIG.
74-Sectional View
of
Air Bypass Valve
exhaust-emitted gases
FIG. 75-289
a n d
302
V-8 Engine With Thermactor Exhaust System