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Page 23
NOTE;
It is important to recheck the ignition timing every time the dwell is
adjusted. A one degree change in dwell causes a one degree change in timing.
THIS TEST DOES NOT APPLY TO ELECTRONIC OR TRANSISTOR IGNITION SYSTEMS EXCEPT
DELCO HEI AND THOSE TYPES USING CONVENTIONAL CONTACT POINTS.
ON HE1
SYSTEMS, THE DWELL ANGLE WILL BE LOW AT iDLE SPEED AND WILL INCREASE STEADILY
AS ENGINE SPEED INCREASES.
IF IT DOES NOT, THE ENGINEMAY
MISFIRE DURING
ACCELERATION AND AT HIGH SPEEDS.
TO CORRECT THIS CONDITION, REPLAC_ THE
ELECTRONIC MODULE IN THE DISTRIBUTOR,
There is a direct relationship between dwell and timing.
However, it is
only a one way relationship.
If you change the dwell angle of the breaker
points, you will automatically change the timing of the ignition.
Changing
the timing, however, has no effect on the dwell angle.
FOR THIS REASON IT
IS IMPORTANT TO RE-CHECK THE TIMING WHEVEVER THE DWELL ANGLE HAS BEEN ADJUSTED.
When the dwell angle is increased, the timing is retarded.
Conversely, when
the dwell angle is decreased, the timing is advanced.
In fact, there is a
one-to-one ratio between dwell and timing.
For every one degree change in
dwell, there is a corresponding one degree change in timing.
This can
sometimes be used to make minor changes in timing.
If, for example, it is
desired to advance the timing two degrees, it canbe
done by reducing the
dwell angle two degrees.
This assumes that the dwell angle will not be
changed out of its specified range.
Due to normal wear of the rubbing bloc_ the normal tendency Is for the
dwell angle to increase.
This, of course, causes the _iming to become retarded
and results in a loss of power and econorRy, if the engine has been properly
tuned initially, restoring the dwell angle to its original setting will
restore the timing to its original setting.
I
/
//
'w°°
TYPICAL
DWELL
8 CYL, ENGINE
_o
49 . _
_
/
W;de Gap
SMALL
DWELL
ANGLE
CAUSES
POOR
HIGH SPEED
PERFORMANCE
Small Gap
LARGE
DWELL
ANGLE
CAUSES POINTS TO BURN
FIGURE 27
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