MSD 8970 Installation

3-Stage Retard

PN 8970

IMPORTANT: Read the instructions before attempting the installation.

Parts Included:

1 - 3-Stage Retard Control 4 - Mounting Screws
4 - Mounting Grommets 6 - Retard Modules, 2°, 3°, 4°, 3-Zero°

WARNING: During installation disconnect the battery cables. When disconnecting the battery,

always remove the negative cable first and connect it last.

Note: The 3-Stage Retard Control must be used with an MSD Ignition Control.

Note: When the Three Stage Retard Control is installed the ignition timing will retard approximately

4° from its original setting. After installation, the timing should be checked and adjusted

as necessary.

OPERATION

The 3-Stage Retard Control can retard the timing three different times and each with an individual
amount. The three amounts are cumulative and the maximum amount of retard is 25°. Each retard
stage is activated when its corresponding activation wire is removed from ground and the retard will
remain activated until the wire is grounded again.
There is also a Start Retard circuit that
will retard the timing 10° or 25° during
cranking to ease starting on engines with
locked-out timing or crank triggers.

CYLINDER SELECT

T h e 3 - S t a ge Ret a r d C o n t r ol is
programmed at the factory for 8-cylinder
engines. It can easily be modified for use
on 4 and 6-cylinder engines. The number
of cylinders is selected by cutting the
Cylinder Select Loops as shown in
Figure 1.

CYLINDERS CUT LOOPS
8 NONE
6 RED
4 RED AND BLUE

Figure 1 Selecting the Number of Cylinders.

MOUNTING

The 3-Stage Retard Control can be mounted under the hood but should
be away from direct engine heat sources. Make sure that the wiring
reaches their connections. Before mounting the control, install the
supplied rubber grommets into the end panels. Then install the sleeve
with the beveled edge facing down (Figure 2).

Use the Control as a template and mark the mounting holes. Use an
1/8” bit to drill the mounting holes.

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Figure 2 Installing the

Vibration Mounts.

2 INSTALLATION INSTRUCTIONS

WIRING

RED

BLACK

YELLOW

This is the On/Off wire. Connects to switched 12 volts.

Connects to Ground.

Trigger output. Connects to the MSD Ignition's White Wire.

TRIGGER INPUTS

There are two input trigger circuits. The wires will never be connected at the same time.

WHITE

GREEN/VIOLET

2-Pin Connector

Connects to points or the amplifier trigger wire.

Connects to the magnetic pickup of the distributor or crank trigger. Green is
negative, Violet is positive.

RETARD CONTROL WIRES

BROWN

ORANGE

GRAY

Retard 1, Activated when removed from ground.

Retard 2, Activated when removed from ground.

Retard 3, Activated when removed from ground.

START RETARD WIRES

VIOLET

This wire activates the start retard. When 12 volts are supplied, the timing is
retarded during cranking.

VIOLET LOOP

This programs the start retard for either 10° or 25° of retard. The unit is
set for 10° at the factory and this loop must be cut to obtain 25°.

The Retard Control wires activate the corresponding retard stage. The retard amount is activated when its
wire is removed from ground. If you do not plan on using each stage, the corresponding wire must
be grounded or a Zero degree module must be installed.
When more than one are activated, the retard is the sum of the modules (6°+4°+8°=18°). The
maximum retard is 25°.

Figure 3 Wiring an MSD 6 Series Ignition with Points/Amplifier.

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INSTALLATION INSTRUCTIONS 3

Figure 4 Wiring an MSD 6 Series Ignition with a Mag Pickup.

Figure 5 Wiring an MSD 7 Series Ignition with Points/Amplifier.

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