Mechanical Operation; Dwell Angle; Distributor Spark Advance Test; Centrifugal Advance - Ford LSG 875 Service Manual

2-24
IGNITION SYSTEM
2-24
MAJOR REPAIR OPERATIONS (Continued)
MECHANICAL OPERATION
1. Turn the switch to the SET position.
2. Adjust the SET TACH control so that ta-
chometer pointer is on the SET line.
3. Turn the switch to the SYNC position and
check to make sure that the drive chuck .is
securely tightened on the distributor shaft.
4. Turn the motor switch to the left for 8 cylin-
der setting.
5. Adjust the speed control to vary the distribu-
tor speed between 400 and 4000 engine
rpm, or at the maximum speed of the engine
on which the distributor is used. Erratic or
thin faint flashes of light preceding the reg-
ular flashes as the speed of rotation is in-
creased can be due to weak breaker arm
spring tension or binding of the breaker arm
on the pivot pin.
6. Operate the distributor at approximately
2500 engine rpm and move the protractor
scale so that the zero degree mark on the'
scale is opposite one of the neon flashes.
The balance of all the flashes should come
within 1 degree, plus or minus, evenly
around the protractor scale. A variation
larger than 1 degree or erratic or wandering
flashes may be caused by a worn cam or
distributor shaft or a bent distributor shaft.
DWELL ANGLE
1. Turn the switch to the CAM position. Oper-
ate the distributor at about 1000 rpm.
2. Turn the test selector switch to the cam an-
gle position and operate the distributor at
approximately 1000 engine rpm.
3. Adjust the breaker point gap until the dwell
angle is to specifications.
DISTRIBUTOR SPARK ADVANCE TEST
The spark advance is checked to determine if
the ignition timing advances in proper relation to
engine speed and load.
1. Check the contact dwell. If the contact dwell
or the breaker point gap is not within specifi-
cations, adjust the breaker points.
2. Check the breaker arm spring tension and
adjust it, if necessary.
CENTRIFUGAL ADVANCE
1. Set the test set to 0 degree advance and the
initial rpm setting listed in the specifications.
2. Operate the distributor in the direction of ro-
tation and slowly increase the rpm to the
setting specified for the first advance read-
ing listed in the specifications.
If the correct advance is not indicated at this
rpm, stop the distributor and bend one spring
adjustment bracket to change its tension. Bend
the adjustment bracket away from the distributor
shaft to decrease advance (increase spring ten-
sion) and toward the shaft to increase advance
(decrease spring tension). After the adjustment
is made, identify the bracket.
3. After an adjustment has been made to one
spring, check the minimum 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 distributor 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.