DISTRIBUTOR POINT DWELL. (See Figure 2)
in timing, requiring re-timing of the distributor
Dwell* or dwell angle is the number of degrees
since the rubbing block of the moving arm will
the distributor shaft rotates measured from the
contact the cam in a different place.
point where the ignition contacts close to the
When a dwell specification is given with a high
point where the y open again. Dwell angle is in-
and low limit, set the point dwell to the lower
versely proportional to point gap, that is, in-
limit for new points to allow for rubbing-block
creasing the gap decreases the dwell, and vice
Insufficient dwell may cause ignition failure at
high speed, while too much dwell increases the
The percent of dwell
total average current which the points must han-
is the percentage of the actual dwell angle of the
dle, particularly at low speed. This usually leads
points as compared to the maximum, dwell angle
to very short point life.
possible (100 percent dwell). The 100 percent
dwell for 4, 6, and 8 cylinder engines, and some
After a distributor is initially timed for a given
e x a m p l e s of percent of dwell are listed in
engine, any change indwell will result in a change
Comparison of percent of dwell and dwell angle
(. 60) (90)
(. 60) (60)
(. 60) (45)
MAINTENANCE OF DISTRIBUTORS.
CONTACT POINT GAP AND DWELL
(Cam Angle Relationship)
It is highly recommended that all the functions
If a distributor cannot be adjusted so that gap and
of a distributor be tested before repair to deter -
mine the amount of repair work required and
dwell are within specifications at the same time
again after repair to make sure that the distrib-
inspect the distributor for the following possibil-
utor is in serviceable condition. The test pro-
a. Improper spring tension or sticky pivot.
cedure in this instruction book is written to
completely test a distributor in logical sequence.
b. Wrong point set installed.
The settings of controls are not re-stated in the
c. Bent shaft, causing point opening to vary on
following test if they are unchanged for that test.
each cam lobe.
For test specifications for a particular distrib-
d. W o r n cam lobes or defective cam, as
utor see the applicable manufacturer's test data.
above. ( Compare gap at each cam lobe if in
ADAPTER FOR TESTING 24 VOLT WATER-
e. Points floating, or not following the cam at
PROOFED DISTRIBUTORS. (See Figure 3)
with the distributor tester for making overall
distributor tests on
In practically every case the remedy will be
24 volt waterproofed distributors without re-