6421 Datasheet, PDF (5/28 Pages) Mallory performance club – The MSD produces full power multiple sparks for each firing of a plug

INSTALLATION INSTRUCTIONS
5
Grounds: A poor ground connection can cause many frustrating problems. When a wire is specified
to go to ground, it should be connected to the battery negative terminal, engine block or chassis.
There should always be a ground strap between the engine and the chassis. Always securely connect
the ground wire to a clean, paint free metal surface.
Ballast Resistor: If your vehicle has a ballast resistor in-line with the coil wiring, it is recommended
to bypass it.
Routing Wires: The MSD wires should be routed away from direct heat sources such as exhaust
manifolds and headers and any sharp edges. The trigger wires should be routed separate from the
other wires and spark plug wires. It is best if they are routed along a ground plane such as the block
or firewall which creates an electrical shield. The magnetic pickup wires should always be routed
separately and should be twisted together to help reduce extraneous interference.
PROGRAMMING
CYLINDER SELECT
The MSD is programmed for operation on 8-cylinder engines.
If installing the Ignition on a different style engine, the number
of cylinders will need to be selected on the Cylinder Select
Rotary Switch (Figure 1).
REV LIMITER
There are two adjustable rev limits that you can adjust; the
Max Limit and the Two Step Limit. Both limits are adjusted in
100 rpm increments by turning the rotary switches on the side
of the Ignition (Figure 2). Note: The engine can be running as
you make adjustments to the rev limiter function.
CYLINDER
COUNT
6
48
CYL
   Figure 1 Programming the Number of
Cylinders.
Max Limit: This is the overrev rpm limit. The Soft Touch circuitry will begin dropping the spark to
cylinders any time the rpm reaches the amount you select, except if the Two Step Limit is activated (12
volts applied to the Blue wire). The limit can be adjusted from 2,000 to 11,900 rpm. Setting both dials
to Zero defaults to a limit of 10,000 rpm. Setting the 1,000's dial to 1 defaults to 11,000 rpm rev limit.
THIS EXAMPLE
SHOWS 2,500
RPM.
THIS EXAMPLE
SHOWS THE
OVERREV AT
6,500.
THIS EXAMPLE
SHOWS 8-CYLIN-
DER ENGINE (FULL
CLOCKWISE).
6
48
CYL
Figure 2 Adjusting the Rev Limits.
   Figure 2 Rev Limiter sample setting.
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