83647 Datasheet, PDF (2/4 Pages) Mallory performance club – MSD HEAT Digital HEI Module

2
INSTALLATION INSTRUCTIONS
8. Connect the long black wire to the engine block for a solid ground.
9. See the next page for tachometer and rev limit programming.
10. It is recommended to install the supplied low resistance rotor bushing. This improves the spark
transfer from the coil to the rotor tip. Remove the coil cover and coil. Replace the rotor bushing.
GRAY
TO TACH
OUTPUT
LONG BLACK
TO ENGINE
GROUND
Figure 2 Connecting the Module and Tach Lead.
TACHOMETER INFORMATION
The HEAT Digital HEI Module has a Gray wire that provides a 12 volt square wave, 20° tachometer
signal that will trigger most tachometers. It is recommended to connect this lead to your tach’s trigger
input wire and check its operation. If the tach requires a higher voltage signal, connect its input wire
to the Tach terminal on the HEI Cap (Coil-/Tach). Note that the rpm limiter is extremely accurate and
due to the variety of tachometers available, there may be differences in the displayed rpm.
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