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9-6
Dimen-
sion
A
B
c
D
E
F
NOTE:
6 Cylinder
1.75
1.136
1.301-1.300
2.520-2.517
3.1
0.516-0.517
8 Cylinder
1.9
1.16
1.559-1.561
4.018-4.021
4.5
0.516-0.517
Missing dimensions according to
individual
test bench.
All dimensions in inches.
BREAKER POINT
RESISTANCE
1. Turn the test selector to the
appropriate position.
2. Revolve the chuck by hand
until the distributor breaker points
are closed.
3. The meter pointer on the cam
angle meter should read in the OK
zone. If the meter pointer does not
fall in the OK zone, there is exces-
sive resistance caused by a faulty
contact across the distributor points,
a faulty primary lead, or a poorly
grounded base plate. A faulty contact
across the distributor points indi-
cates improper spring tension or
burned or pitted points.
INSULATION AND LEAKAGE
1. Turn the test selector to the
cam angle position and
revolve
the
chuck by hand until the distributor
breaker contacts are open.
2. The cam angle meter should
show
a zero
reading.
If
a zero read-
ing is
not obtained, a short circuit to
ground exists.
A short could be caused by poor
primary lead wire
insulation,
a
shorted condenser, or a short be-
tween the breaker arm and breaker
plate.
MECHANICAL OPERATION
1. Turn the test selector to the
SYNCHRO. position and check to
make
sure
the drive chuck is securely
tightened on the distributor shaft.
2. Turn the motor control switch
to the setting for an eight cylinder
car or for a six cylinder car.
If it Is necessary to reverse the ro-
tation of the drive motor, tum the
motor control switch to the OFF po-
sition and allow the chuck to come
to a complete stop before reversing
the switch.
3. Adjust the rpm control to vary
the distributor speed between 400
and 4000 engine rpm or at the maxi-
GROUP
9-
IGNITION SYSTEM
mum speed of the engine on which
the distributor is used. Erratic or thin
faint flashes of light preceding the
regular flashes as the speed of rota-
tion is increased can be due to weak
breaker arm spring tension or bind-
ing of the breaker arm on the pivot
pin.
4. Operate the distributor at ap-
proximately 2500 engine rpm.
5. Move the protractor scale with
the adjustment control so that the
zero degree mark on the scale is op-
posite one of the neon
flashes.
The
balance of all the flashes should come
within 1
o,
plus or minus, evenly
around the protractor scale. A varia-
tion larger than 1
o
or erratic or wan-
dering flashes may be caused by a
worn cam or distributor shaft or a
bent distributor shaft.
DWELL ANGLE
1. Turn the cylinder selector to
the figure corresponding to the num-
ber of lobes on the cam of the dis-
tributor being tested.
2. Turn the test selector switch to
the cam angle position and operate
the distributor at approximately
250 engine
rpm.
3. Adjust the distributor breaker
point gap to the dwell angle shown in
the specifications.
BREAKER PLATE WEAR
A worn breaker plate on the dual
advance distributors will cause the
breaker point dwell to change as
engine speed and load condition
are varied.
On the dual advance distributor
adjust the test set to 0
o
advance,
0 inches vacuum, and 250 rpm.
Adjust the dwell angle to specifica-
tions. Apply vacuum to the distribu-
tor diaphragm and increase it very
slowly while observing the indicated
dwell angle. The maximum dwell
angle variation should not exceed 6
o
when going from zero to maximum
vacuum at constant rpm. If the dwell
angle variation exceeds this limit,
there is excessive wear at the
stationary subplate pin or the dia-
phragm.
DISTRIBUTOR SPARK
ADVANCE
The spark advance is checked to
determine if the ignition timing ad-
vances in proper relation to engine
speed and
load.
Dual Advance Distributor
1. Check the contact dwell. If the
contact dwell is not within specifica-
tions, adjust the breaker points.
2. Check the breaker arm spring
tension and adjust
it if
necessary.
The dual advance distributor has
two independently operated
spark
advance systems.
Each system
is ad-
justed separately. Adjust the centrtf·
upl advance before adjusting the
vacuum advance.
Centrifugal
Advance
1.
Operate the
distributor in the
direction of
rotation and adjust the
speed
to
the initial
rpm setting listed
in the
specifications.
Move the pro-
tractor
scale so that one of the flashes
lines up with
the zero degree mark.
2. Slowly
increase the rpm to the
setting specified
for the first advance
reading
listed in the specifications.
If the correct
advance is not indi-
cated at this rpm,
stop the distribu-
tor and bend one
spring adjustment
bracket to change
its tension (Fig.
7. Bend the adjustment bracket
away from the distributor
shaft
to decrease advance (increase
spring tension) and
toward
the
shaft to increase advance
(de-
crease spring tension).
Mter the
adjustment
is
made,
identify the
bracket.
3. After an adjustment
has been
made to one spring,
check
the
mini-
mum advance point
again.
4. Operate
the
distributor
at the
specified rpm
to
give
an
advance
just
below the
maximum.
If this advance
is not to specifications,
stop the dis-
tributor and bend
the
other
spring
bracket to give
the correct advance.
5. Check the
advance at all rpm
settings listed
in the specifications.
Operate the distributor
both up and
down the rpm
range.
Vacuum Advance
1. Connect
the
test
set vacuum
line to the fitting on
the diaphragm.
2. Set the test
set to
0
o
advance,
0 vacuum, and at 250 rpm.
3. Check the advance
at the first
vacuum setting given
in the specifi-
cations.
4. On 8 cylinder
single diaphragm
distributors,
if the
advance
is in-
correct, change the calibration
wash-
ers between the
vacuum chamber
spring and out
(Fig.
8).
After install-
ing or removing the washers,
position
the gasket in place
and tighten the
nut. The addition of a washer will
decrease advance and
the re-
moval of a washer
will increase
advance.
5. After one vacuum setting
has
been adjusted, the others
should
be
checked. Do not change the orig-
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