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8-48
IGNITION SYSTEM
and pull in a straight line at a right angle to the
contact surfaces (Fig. 1 3 ) . Take a reading as the con-
tacts start to separate under the slow and steady pull
of the scale. Spring tension should be 17 to 20
ounces. If the reading is outside these limits, loosen
the screw which holds the end of the breaker arm
spring, and slide the end of the spring in or out, as
necessary.
(2)
Tighten the screw and measure the spring ten-
sion.
NOTE: Spring tension that is too great, will cause
excessive wear on the distributor cam and on the
nylon block of the movable contact arm. Spring
tension that is too weak, is unable to keep the con-
tacts in contact with each other when they close.
this is
particularly true as engine speed is increased,
causing high-speed misfiring.
INSTALLING AND ALIGNING
CONTACTS
(1) Loosen the terminal screw nut, and remove
the primary lead, condenser lead and terminal screw.
(2)
Remove the stationary contact lock screw and
remove the old contact set.
(3) Install a new contact set; the sleeve at one
end of the adjustable bracket fits over and pivots
on the upper breaker plate mounting pin, the con-
tact insulator also retains the terminal screw head.
(4)
Connect the condenser and primary leads.
(5)
Align the contacts,
if
necessary, to obtain con-
tact in the center of the contacts, by bending the sta-
tionary contact bracket only.
Never bend
the mov-
able contact arm to obtain alignment.
(6) After aligning the contacts, adjust contact clear-
ance to "Specifications," using dial indicator (Fig.
1 4 ) . Recheck the contact arm spring tension.
(7) Test the dwell angle to show proper degree of
closure. See Paragraph, "Distributor Contact Dwell."
The lock screw should be loosened just enough
so
that the stationary bracket can be removed with a
slight drag; otherwise it will be difficult to set the
contacts accurately. After setting the contacts to the
correct gap, tighten the lock screw.
DISTRIBUTOR LUBRICATION
(1) Add 3 drops of SAE 1OW oil to the oiler on the
outside of distributor base.
(2)
Lubricate the felt wick under the rotor in top
of distributor cam with 3 to 5 drops of SAE 1OW oil.
(3) Wipe all old grease from surface of the distrib-
utor cam. Apply a light film of new distributor cam
lubricant number 1473595.
CAUTION: Do not over-lubricate. Excess grease
will
be
thrown from the distributor cam when the
engine is running.
If
this grease strikes the contacts,
arcing and burning of the contacts will result.
TESTING DISTRIBUTOR ADVANCE
Centrifugal Advance Curve
Carefully mount the distributor assembly (less cap
and rotor) in a reliable stroboscope-type distributor
tester
so that gear is not damaged and proceed with
tests as follows:
(1) Turn the Tach-Dwell switch to the 6 LOBE posi-
tion and the Motor Switch to the correct direction of
rotation. Refer to "Distributor Advance Specifica-
tions" in this manual.
(2)
Turn the battery switch "ON."
(3)
Regulate the tester speed control to operate dis-
tributor at 100 distributor rpm.
(4) Hold the distributor contact plate in the full
retard position and align the "0" of the distributor
tester degree ring with any of the arrow flashes.
(5) Adjust the tester speed control to operate the
distributor at speeds call'ed for under "Specifications"
and observe arrow flashes opposite tester degree ring
to determine degrees of advance.
(6)
If the advance is not according to specifica-
tions, corrections can be made by bending either
the light or heavy governor weight spring tabs on the
cam yoke to increase or decrease spring tension. Ad-
just the light spring tension to obtain the first two posi-
tions shown in the specifications; adjust the heavy
spring tension to obtain the last two positions. The
governor spring tabs can be reached through the ac-
cess hole at the contact plate. Rotate the shaft until
the proper spring and tab line up with the access
hole. Insert a screwdriver blade through the access
hole and bend the spring tab toward the distributor
cam to decrease the spring tension and advance the
spark, or away from the distributor cam to increase
spring tension and retard the spark.
NOTE: The light tension spring controls the lower
end of the advance curve, and the heavier spring
controls the upper end of the advance curve.
Vacuum Diaphragm Leak Test
With the distributor mounted in Distributor Tester
and with vacuum unit attached to the distributor,
proceed as follows:
(1) Place thumb over end of vacuum pump hose
and adjust the regulator control knob to give a read-
ing of 20 inches of vacuum with the hose closed off
to be sure the tester hose does not leak.
(2) Attach the tester vacuum pump hose to the tube
on the vacuum unit. Vacuum gauge should hold on
maximum vacuum obtainable
if
no leaks exist.
(3)
Observe the breaker plate
while
performing the
leak test, to test the response of the breaker plate.
There should be instant response to the pull of the
diaphragm, moving the plate without a drag, bind
or jerk in either direction.
(4)
If leakage
is
indicated, replace the vacuum
unit assembly.
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