MSD 8970 Three Stage Retard Control Installation - Manual (Page 7)

INSTALLATION INSTRUCTIONS 
M S D I G N I T I O N
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STaRT RETaRD
The Start Retard function is set up at the factory to retard the timing 10° during cranking. It can
be modified to retard 25° by cutting the Violet wire loop (Figure 12). The timing will be retarded
from the set mechanical amount of the distributor or crank trigger position.
The Violet wire is responsible for activating the Start Retard circuit. When activated, the Start
Retard function will retard the timing 10° or 25° while the engine is cranking. There are two
ways to connect this circuit:
a. Constant 12 Volts
In this setup the Violet wire is connected to a switched 12 volt source. Whenever the ignition is
turned On, 12 volts is applied and the retard function is activated. The retard will be deactivated
when the engine reaches approximately 1,300 rpm and will not occur again until the ignition
is turned Off (or drops below 400 rpm).
B. Cranking Only:
In this setup, the timing is retarded only when the engine is cranking. Connect the Violet wire
directly to the starter solenoid. When the key is turned to the Crank position, 12 volts is applied
to the Violet wire, activating the retard. When the key is released, 12 volts is removed and the
timing returns to your run timing.
Note: The Start Retard circuit overides the three retard stages.
Figure 12 Wiring the Start Retard Function.