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(335)
ELECTRICAL SYSTEMS
IGNITION SYSTEM
10-59
and to rotate the breaker plate in a clockwise
direction. This moves the contact points so that
the Iistributor cam lobes open the points
earlier in the compression stroke. The amount
of throttle opening determines, in part, the
amount of intake manifold vacuum and thus
the amount of spark advance
obtained.
The
advance obtained by the vacuum control is
added to the advance obtained by the cen-
trifugal advance mechanism, as shown in
figure 10-68.
indicator,
No.1
terminal on light
switch, igni-
tion switch, ignition coil and distributor.
If
any
connections are loose, disconnect and clean
terminals thoroughly, then connect and tighten
securely. Check wiring insulation and repair
any breaks with tape.
b. Centrifugal and Vacuum Advance
Mechanisms
1.
Remove distributor cap. Turn the rotor
in a counterclockwise direction until advance
FLYWI-EEL DEGREES
42
~--40 ---- --36
38
- - -
3
6
- - -
-- -
32
34
~--
3 2
------28
30
-
--2
8
- - -
-- -
24
2
8
-
- - 24- - - -- -
20
22
- - -
---20-----16
18-
-
18-
-
12
,
I
1
I
VACUUM ADVANCE RANGE I
t·
PRODUCTION LIM
ITS
ARE PLUS OR
MINUS
,.
(PART
THROTTLE)
VACUUJ.4 ADVANCE
PLUS
CENTRIFUGAl
14
- - -
--
12-
-
8
1
0
-
-
8 -
- 4
(FULL THRO TTLE) CENTRIFUGAL. ADVANCE CURVE
PRODUCTION
lIt.4ITS ARE PLUS OR hllNUS 2°
6
-
- 4 -
- 0
o
U.O.C.-
o
U.D.C
.
-
400
I
10
800
1
200
20
1600
2000
2400
2800
3200
3600
4000
4250
ENGINE RPM
I
30
40
50
60
70
80
APPROXNATE MILES PER HOl..J\
Figure 10-68-Distributor Spark Advance Chart-All Ser
ies
10-44 PERIODIC INSPECTION OF
IGNITION SYSTEM
The best assurance of obtaining maximum
service with minimum trouble from the igni-
tion system is to follow a regular inspection
procedure at periodic intervals and to correct
any sub-normal conditions disclosed by the
inspect ion. Lubrication of the distributor is
covered under Periodic Lubricare
Instructions
(par.
1-1
and 1-3)
.
The following inspection
procedure
will disclose any sub-normal condi-
tion in ignition system that requires correction.
a. Battery and Primary Circuit Wiring
1.
Check battery and cables to make sure
ignition system has a dependable source of
energy (par. 10-17).
2. Check primary circuit wiring connec-
tions at cranking motor solenoid switch, charge
weights are fully extended, release rotor and
allow springs to return
weights
to
retard posi-
tion. Repeat several times.
If
springs
do not
return weights to stop without sticking, or
there is excessive free movement of rotor and
cam in the re
tard
position, remove
distributor
for
correction.
2. Rotate breaker plate by
pushing
against
condenser and note whet her spr ing in vacuum
control unit r
eturns
br eaker plate to full retard
position. On 1948 model distributor, note
whether movement of plate. is
rough,
which
may be due to dirty or loose balls or indenta-
tions worn in breaker plate or distributor
hous-
ing. An additional test of breaker plate action
under operating conditions is given in
para-
graph 10-45.
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