Oil Bath Type; Flame Arrestor; Evaporation Control System - Chevrolet 10 1971 Series Chassis Service Manual

Inspect air cleaner at 12,000 miles for dust leaks,
holes or other damage, replace if necessary. If condi­
tion is satisfactory, rotate element 180° from originally
installed position.
Replace at 24,000 miles.
Oil Wetted Paper Element with
Polyurethane Wrap
This dual element air cleaner has extremely long life
and will not require replacement for 50,000 to 100,000
miles under normal operating conditions.
Cleaning and oiling of the polyurethane wrap should be
done at 24,000 miles under normal highway or city-type
operation. Service under off-the-road or extremely dusty
operations should be performed at 12,000 miles or less
depending upon severity of operating conditions.
To clean: Remove polyurethane wrap from paper ele­
ment, wash in suitable solvent to remove oil and dirt.
Squeeze dry, dip in engine oil and squeeze to remove ex­
cess oil (never shake or wring— always squeeze). Wrap
element in clean dry cloth and squeeze out any remaining
oil.

Oil Bath Type

Check every 12,000 miles, clean if necessary, and re­
fill with engine oil, SAE 50, when temperature is above
freezing and SAE 20 below freezing.

Flame Arrestor

Clean the arrestor every 12,000 miles.
Crankcase Ventilation Filter (Located within
Air Cleaner)
If so equipped, inspect at every oil change and replace
if necessary. Replace at least every 24,000 miles; more
often under dusty driving conditions.
EM ISSION CONTROL SYSTEMS
Positive Crankcase Ventilation (P.C.V.)
All General Motors gasoline engine powered vehicles
are equipped with Positive Crankcase Ventilation— a sys­
tem which permits no crankcase emission to be dis­
charged into the atmosphere. To function properly, the
system depends on the PCV Valve which returns blow-by
gasses to the combustion chamber where they are burned.
Maintenance
This valve must be clean in order to maintain efficient
engine operation. An inspection of the ventilation filter
should be made at the first oil change (4 months or 6,000
miles, whichever occurs first). At each subsequent oil
change, the ventilation filter should be inspected and re­
placed if necessary. Replace filter at least every 24,000
miles. Under normal driving conditions, the PCV Valve
should be replaced every 24 months or 24,000 miles,
whichever occurs first, and all hoses and fittings should
be inspected and cleaned or replaced, as necessary. Re­
place the PCV valve and inspect related parts every 12
months or 12,000 miles when the vehicle is used in a
service requiring more frequent engine oil change as
covered under " Engine Oil Change Interval".
Controlled Combustion System (C.C.S.)
The Controlled Combustion System is entirely separate
from the Positive Crankcase Ventilation System and is
designed to reduce pollutants in the exhaust by altering
the combustion process. CCS is a combination of design
features including a special air cleaner which incorpo­
rates thermostatic control of heated air to the carbure­
tor, a special calibrated carburetor and distributor and a
modified combustion chamber design.
Complete effectiveness of the system, as well as full
power and performance, depend upon engine idle speed,
ignition timing, and dwell being set according to the
specifications shown on a label under the hood. These
adjustments should be checked at the first oil change (4
months or 6,000 miles, whichever comes first). Subse­
quent checks should be made at 12 month or 12,000 mile
intervals, whichever comes first. These adjustments are
also included as part of the quality tune-up recommended
at the same intervals.

Evaporation Control System

All General Motors passenger cars and series 10
trucks are equipped with an Evaporation Control System.
This system is designed to minimize the escape of fuel
vapors to the atmosphere. Included in the system are a
special fuel tank, liquid-vapor separator, carbon canis­
ter, canister purge hoses, and carburetor modifications.
Fuel vapors which would otherwise escape to the atmo­
sphere are directed into the carbon canister. The carbon
absorbs the vapors and stores them. The vapor is re­
moved from the canister during periods of engine opera­
tion as manifold vacuum draws the vapors into the
engine and burns them.
For proper system performance, periodic canister fil­
ter servicing is required. Every 12 months or 12,000
miles, whichever comes first, (more often under dusty
conditions) the filter in the base of the canister should
be replaced and the canister inspected.
The General Motors Evaporation Con­
NOTE:
trol System is designed to control evaporation
losses from your vehicle under normal condi­
tions using 9 lb. Reid Vapor Pressure fuel
specified by Federal and California test re­
quirements. However, if you should use fuel
of abnormally high volatility for existing tem­
perature conditions, you may detect a gasoline
odor during or after driving in heavy traffic. If
you find this objectionable, you may prefer to
use a lower volatility fuel.
Should it ever be necessary to replace
NOTE:
the fuel tank cap, use only the specified cap.
ENGINE TUNE-UP A N D
ELECTRICAL SYSTEM CHECKS
The above emission control system checks also are
included in engine tune-ups which are recommended at
one year or 12,000-mile intervals.
Drive Belts
Every 6000 miles — Inspect drive belts for wear,
fraying, cracking, and tension. Belts which are in poor
condition should be replaced immediately.
LUBRICATION 0-9
10-30 CHEVROLET TRUCK SERVICE MANUAL