Chevrolet 70 1969 Series, Руководство по ремонту

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GASOLINE ENGINES 6A-3
may be a head gasket leak between the cylinders.
This condition could be cause of coolant leaking
into cylinders.
N O T E : An engine with low or uneven com ­
pression cannot be tuned to givepeakperformance;
therefore, it is important to make necessary cor­
rections before proceeding with tune-up operations.
SER V IC E A N D IN S T A L L SPARK PLUGS
1. Inspect all spark plugs carefully. Look for
glazed, broken, or blistered porcelains and burned
electrodes. Refer to "G A S O L IN E EN G IN E TUNE-UP
C H A R T " later in this section for correct type of
spark plugs used in these engines.
2. If sparkplugs are serviceable, use an abra­
sive type cleaner such as sand blaster to thorough­
ly clean spark plugs. File end of center electrode
flat.
3. Adjust spark plug gaps to specifications.
4. Test spark plugs with spark plug tester if
available.
5. Install spark plugs using new gasket. Use
torque wrench and special spark plug socket
wrench. Correct torque for spark plug installation
is 23 to 27 foot-pounds.
IGNITION S Y S T E M S ER V IC E
1. Remove equipment as required to provide
access to ignition distributor, spark plug wires
and coil.
2. Check condition of wiring. If any wires are
brittle, cracked, or otherwise damaged, replace
as necessary.
3. Inspect distributor cap for burned wire
sockets, cracks, and for errosion at terminals in­
side cap. Replace the distributor cap if it is not in
good condition. When installing spark wires, refer
to figure 3 which shows cylinder numbering, firing
order and distributor cap wire socket numbering.
4. Refer to E N G IN E E L E C T R I C A L (SEC. 6Y)
and inspect ignition distributor points, rotor, and
advance mechanism. Make necessary parts re­
placement and/or adjustments.
B A T T E R Y A N D B A T T E R Y C A B L E SER V IC E
1. Using battery hydrometer check specific
gravity of storage battery electrolyte in each cell.
Gravity reading below 1.230 (corrected to 80°F.)
indicates insufficient charge.
2. Use a voltmeter to check cranking voltage.
Disconnect coil primary lead from negative term­
inal on coil to prevent engine from firing during
test.
3. With voltmeter connected between coil posi­
tive terminal and ground, operate starter. Voltage
of 9 volts or more when starter is cranking engine
indicates that battery and ignition circuit to coil
are satisfactory. If voltage reading is less than 9
volts when engine is being cranked, or if cranking
Figure 3— Cylinder Number and Spark Plug Wire Locations
speed is low, a weak battery, defective starter
switch, or excessive resistance in ignition circuit
exists.
N O T E : If, when making check of cranking volt­
age, it is noted that cranking speed is uneven, this
is indication of uneven cylinder compression, de­
fective starter or starter drive.
4. In cases where loose, corroded, or other­
wise defective battery cables and/or wiring are
found, the defects must be corrected to insure
good engine performance.
5. If battery is weak or shows other evidence
of being defective, refer to appropriate coverage
in E N G IN E E L E C T R I C A L (SEC. 6Y) in this manual
for method of diagnosing battery deficiencies.
C H E C K IN G D R IV E B E LTS
1. Inspect drive belts for excessive wear and
damage. If no defects are found, check belts for
proper tension.
2. When installing new drive belts or adjust­
ing old belts use tension gauge to provide correct
tension.
C A U T IO N : Adjusting drive belts too tightly
will impose too great a load on bearings in the
driven units. Slipping will occur if drive belts are
not adjusted tight enough. Belt life will be shortened
if belts are not properly tightened.
C Y L IN D E R H E A D B O L T T O R Q U E A N D
V A L V E L A SH A D J U S T M E N T
A check of cylinder head bolt torque should
be made at regular tune-up intervals and should
be followed by valve lash adjustment. Follow pro­
cedure given below to tighten cylinder head bolts
and adjust valve lash.
1. Run engine until normal operating temper­
ature is reached, then stop engine and remove
rocker arm covers.
2. Referring to figure 4 use torque wrench to
CHEVROLET SERIES 70-80 HEAVY DUTY TRUCK SHOP MANUAL