Chevrolet Light Duty Truck 1973 Service Manual page 342

6 -6 ENGINE
Fig. 8—Checking Fan Belt Tension
detect internal or external leaks within the
cooling system.
SERVICE CRANKCASE
VENTILATION (FIG. 1 1 )
All engines have a "Closed Positive" ventilation system
utilizing manifold vacuum to draw fumes and contami­
nating vapors into the combustion chamber where they
are burned. Since it affects every part of the engine,
crankcase ventilation is an important function and
should be understood and serviced properly.
In a "Closed Positive" ventilation system, air is drawn
through the engine crankcase (through a regulating
valve) (fig. ) into the manifold, drawing crankcase
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vapors and fumes with it to be burned. The "Closed
Positive" ventilation system draws clean air from the
carburetor air cleaner and has a nonvented oil filler cap.
1. Ventilation valve should be replaced at intervals
specified in Section 0.
2. Inspect for deteriorated or plugged hoses.
3. Inspect all hose connections.
4. Remove flame arrestor and wash in solvent, then
dry with compressed air.
5. Inspect ventilation filter (fig. 13) and replace if
necessary.
SERVICE AIR INJECTION
REACTOR SYSTEM
Inspect air injection reactor system for evidence of leaks,
deteriorated hoses, cracked air manifolds or tubes and
loose hose clamps. Inspect air injection pump belt
Fig. 9—Manifold Heat Control Valve (L6)
Fig. 10—Manifold Heat Control Valve (Typical V8)
condition and tension. Make all necessary repairs as
outlined in "Section T " .
6
Because of the relationship between "Engine Tune U p"
and "Unburned Exhaust Gases", the condition of Engine
Tune Up should be checked whenever the Air Injection
Reactor System seems to be malfunctioning. Particular
care should be taken in checking items that affect fuel-
air ration such as the crankcase ventilation system, the
carburetor and the carburetor air cleaner. Carburetors
and distributors for engines with the Air Injection
Reactor System and Controlled Combustion System are
designed, particularly, for these engines; therefore, they
must not be interchanged with or replaced by a
LIGHT DUTY TRUCK SERVICE MANUAL