Chevrolet 10 Series 1970, Service Manual

Page: 14 / 671

LUBRICATION 0-12
engine idle becom es too slow o r rough, the ven­
tila to r va lve should be checked b efo re any
ca rb u retor adjustments are made to compensate
fo r the trouble.
A ir Injection Reactor System (A .I.R .)
The A ir Injection R e a c to r system is designed to reduce
a ir pollution caused by exhaust em ission s. It is en tirely
separate fro m the P o s itiv e Crankcase V entilating system .
The A ir Injection R ea cto r system op erates by oxidizin g
(o r buring) the hydrocarbons and carbon monoside as
they a re expelled fro m the combustion cham ber into the
exhaust. A p o sitive displacem ent a ir pump, driven by the
engine, com p resses clean filte r e d a ir, which is d is trib ­
u t e d and injected at the exhaust port o f each cylin der.
T h is fre s h a ir m ixes with the hot exhaust gases and p r o ­
m otes further oxidation (o r burning) o f both hydrocarbons
and carbon monoxide by converting som e o f them to c a r­
bon dioxide and w ater. T h is does not reduce the danger
o f inhaling carbon monoxide in confined a rea s. Supple­
menting the a ir pump a sp ecial calibrated carb u retor and
distribu tor plus rela ted components a re requ ired.
The A ir Injection R ea cto r system should have the
A .I.R . pump d riv e b elts inspected fo r w ear and tension
e v e ry 12 months o r 12,000 m ile s , w hichever occu rs firs t.
In addition, com plete effe c tiv e n e s s o f the system , as w ell
as full pow er and p erform a n ce, depends upon engine idle
speed, ignition tim ing, and idle fuel m ixture being set
accordin g to sp ecification . A quality tune-up which
includes these adjustments should be p erfo rm e d p e r io d i­
c a lly to assure norm al engine efficien cy , operation and
p erfo rm a n ce.
Controlled Combustion System (C.C.S.)
The C on trolled Combustion System is designed to r e ­
duce a ir pollution fro m exhaust em ission s by im provin g
combustion e ffic ie n c y . It is en tirely separate fro m the
P o s itiv e Crankcase Ventilating system . T h is is done by
p rovid in g heated a ir to the ca rb u retor which p erm its
running on lea n er m ixtu res fo r im proved combustion.
O ther engine m odification s consist o f a sp ecial c a li­
b rated ca rb u retor and distribu tor and related com po­
nents. Com plete e ffe c tiv e n e s s o f the system , as w ell as
fu ll pow er and p erform a n ce, depends upon engine idle
speed, ignition tim ing, and idle fuel m ixture being set
accord in g to sp ecification . A quality tune-up which in­
cludes these adjustments should be p erfo rm e d p e r io d i­
c a lly to assure norm al engine effic ie n c y , operation and
p erfo rm a n ce.
Transmission Controlled Spark (T.C.S.)
P ro c e d u re s fo r checking the operation o f this system
a re outlined in Section 6T o f this manual.
T h is is an e le c tric a lly -o p e ra te d system that elim in ates
the d istrib u tor vacuum spark advance in a ll forw ard
tra n sm ission gea rs (o r ranges, fo r autom atics) except
high fo r a sign ifican t reduction o f hydrocarbon and carbon
m onoxide em ission s. T o do this, a transm ission-m ounted
sw itch con trols a solenoid va lve which regu lates mani­
fo ld vacuum to the distribu tor; during operation in the
low g e a rs (o r ran ges) the solenoid va lve reduces vacuum
supply to the d istrib u tor fo r a retard ed spark condition;
during high g e a r the solenoid valve a llow s full m anifold
vacuum to the d istrib u tor fo r advanced spark. Cold start
conditions a re m et by means o f an o v e r r id e switch. When
the engine is cold, this w ater tem perature sensitive
sw itch circum vents norm al operation o f the system by
d ire c tly activating the solenoid va lve fo r advanced spark.
On some engines a “ Hot” o v e rrid e term in al is combined
with the switch to allow vacuum advance i f engine tem ­
peratu res r is e above 232°F.
Evaporation Emission Control (E.E.C.)
T h is system is designed to reduce fuel vapor em ission
that norm ally vents to the atm osphere fro m the gasoline
tank and ca rb u retor fuel bow l. E v e ry 12 months o r 12,000
m iles, w hichever occu rs fir s t, (m ore often under dusty
conditions), the filte r in the base o f the can ister must be
rep laced and the canister inspected. A ll other parts are
s e rv ic e d as a com plete replacem ent as outlined in S ec­
tion 8.
ENGINE TUNE-UP, EMISSION CONTROL A N D
ELECTRICAL SYSTEM CHECKS
Fuel and e le c tr ic a l system s a re subject to w ear and
contamination and req u ire p erio d ic cleaning and adjust­
ments to maintain maximum econom y and p erform an ce.
P r o p e r adjustment o f engine id le speed, idle fuel m ix ­
ture, ignition tim ing and operation o f the P o s itiv e Crank­
case Ventilation V alve (P C V ) a re im portant to control
hydro-carbon and CO em ission s within governm ent le g ­
isla ted le v e ls . These adjustments and an operational
check o f the P C V V alve should be made at the fir s t o il
change (4 months o r 6,000 m iles, w hichever occurs fir s t ).
The above fuel and e le c tr ic a l system checks also a re in­
cluded in engine tune-ups which a re recom m ended at one
y e a r o r 12,000-m ile in terva ls.
M an ifo ld H eat Control V a lv e
Check m anifold heat control va lve fo r freed om o f op­
eration . If shaft is sticking, fre e it up with GM M anifold
Heat Control Solvent o r its equivalent.
D rive Belts
E v e ry 6000 m iles — Inspect d riv e b elts fo r w ear,
fra yin g, cracking, and tension. B elts which a re in poor
condition should be replaced im m ediately.
Check tension by applying m oderate thumb p ressu re
midway between pu lleys. I f the cen ter to center distance
between pu lleys is 13 to 16 inches, the b elt should d eflect
1/2 inch. If the center to center distance is 7 to 10
inches, the b elt should d eflect 1/4 inch. L oo se belts
should be retensioned to g iv e the c o r r e c t deflection .
Electrical System
CAUTIO N: Headlamp aim s h o u l d also be
checked p erio d ic a lly . It is im portant that any
malfunctions be c o rre c te d prom ptly fo r safety.
Distributor
C o r r e c t distribu tor point gap is v e r y im portant. The
d istrib u tor points a re cleaned and adjusted as p art o f a
good engine tune-up. If th eir condition is questioned,
r e le a s e the distribu tor cap clam ps, rem ove cap and lift
o ff ro to r. Separate the points and inspect them fo r
being badly burned. Clean the points with a b rea k er
point file . If the points do not clean up with a few strokes
CHEVROLET TRUCK SERVICE MANUAL