Chevrolet 70 1969 Series, Shop Manual

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ENGINE ELECTRICAL 6Y-18
IN SPECTIO N A N D C L E A N IN G
Inspect plugs for cracked porcelain and burn­
ed points, and check point gap. Also check for loose
terminals. Replace plugs which have excessively
burned electrodes or cracked porcelain. Plugs
should be cleaned with an abrasive type cleaner.
If porcelain is badly glazed or blistered, the spark
plugs should be replaced. All spark plugs must be
of the same make and number of heat range. Use
a wire feeler gauge when checking spark plug gap.
POINT GAP A D J U S T M E N T
Setting spark plug gap is a precision operation
and should be treated as such. Refer to "Specifica­
tions" at end of this section for proper gap dimen­
sions. All plugs must be set to the same dimension,
using a standard round feeler gauge.
C A U T IO N : Before adjusting gap, file center
electrode flat. In adjusting the spark plug gap,
never bend the center electrode which extends
through the porcelain center as this may break the
lower insulator. Always make adjustment by bend­
ing the ground or side electrode.
SPARK P L U G IN S T A L L A T IO N
Be certain that the old gasket is removed be­
fore installation of plug and that the gasket seat is
clean and smooth. Also check that the spark plug
threads and the cylinder head threads are not dirty
or damaged. Dirty or damaged threads cause a
faulty torque reading, resulting in incorrect in­
stallation and consequent poor spark plug life and
faulty operation.
Install spark plugs in the engine with new gas­
kets and tighten finger-tight. Using special spark
plug wrench socket (S-9704B) as shown in figure 7,
and a torque wrench, tighten plugs to 23-27 foot­
pounds torque.
IM P O R T A N T : It is important that the special
socket be used in torqueing plugs, as an ordinary
socket will bind against cylinder head and give a
false torque reading.
Spark plugs which are not tightened correctly
will result in too high an operating temperature
if too loose, or distortion of the spark plug body
and change in gap setting or damage to the gasket
if too tight.
HIGH AND LOW TENSION WIRES
High tension wires include the wires connect­
ing the distributor cap to the spark plugs, and the
wire connecting the center electrode of the distrib­
utor cap to the center terminal of the ignition coil.
Low tension wires are the small wires connected
to the primary terminals on the coil, and to the
primary terminal at the distributor.
High tension wires have a built in resistance
of approximately 4,000 ohms per foot except coil
wire which is 8,000 ohms per foot. When replacing
wires, make sure proper wires are used.
At regular intervals the wires should be in­
spected for damage. If insulation is cracked or
swollen, wires should be replaced.
IGNITION SYSTEM SPECIFICATION
ri.niiir 401 M
EN GIN E
47SM
D IS T R IB U T O R
M ake....................................................................................... Delco-Remy
Model No................................................................................ 1110478
Rotation (Viewed at Rotor)................................................. Clockwise
Point Opening
N ew ..................................................................................... 0.019"
U sed.................................................................................... 0.016"
Cam Angle (d eg rees).......................................................... 31°—34° (1 )
Centrifugal Advance(3)
Start (d egrees)................................................................. 0—3
RPM ................................................................................ 550
First Intermediate (d eg rees)......................................... 2.7—5.7
RPM ................................................................................ 700
Second Intermediate (d egrees)..................................... 4.3—6.3
RPM ................................................................................ 800
Maximum (d eg rees)........................................................ 1 0 -1 2
RPM ................................................................................ 1750
Firing O rd er........................................................................... 1 -6-5-4 3-2
Ignition Tim in g ..................................................................... 10° BUDC
D ISTR IB U TO R VACUUM CONTROL
M ake......................................................................................... Delco-Remy
Model No..................................................................................
1115356
Inches of Mercury to Start Advance.................................. 3 —5
Inches of Mercury for Maximum A d vance....................... 7—9
Maximum Advance (Engine D egrees)(4)........................... 15
IGNITIO N COIL
M ake......................................................................................... Delco-Remy
Model........................................................................................
1115161
SPA R K PLUGS
M ake......................................................................................... AC
Typ e.......................................................................................... CR-43N
S iz e ............................................................................................ 14 MM
Point Gap ( I n .) ........................................................................ 0.035
Torque (F t. L b s .).................................................................... 2 3 - 2 7
(1 ) Set With Vacuum in Retard Position.
(2 ) Satisfactory Range. When adjusting set to 30 degrees.
(3 ) Specifications listed are distributor degrees and distributor RPM which are one-half engine degrees and
engine RPM.
(4 ) Plus or Minus one degree
CHEVROLET SERIES 70 -80 H EAVY DUTY TRUCK SH O P M A N U A L