MSD 7805 Installation

MSD-8 Plus Ignition

PN 7805

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Note: Solid Core spark plug wires cannot be used with an MSD Ignition.

Parts Included:

1 - MSD-8 Plus Ignition
1 - Mag Pickup Extension Harness, PN 8860
4 - Vibration Mounts and Hardware
4 - RPM Modules: 3K, 7K, 8K and 9K

WARNING: Before installing the MSD Distributor, disconnect the battery cables. When disconnecting

the battery cables, always remove the Negative (-) cable first and install it last.

1 - PN 8830 Filter
1 - Coil Harness
1 - Power Harness
1 - Parts Bag, Mounts, Terminals, etc.

FEATURES

SINGLE OR DUAL COIL OUTPUT

The MSD-8 Plus Ignition Control is intended for racing use only. The Ignition has the ability to be
used with single or dual coil systems. Note that when using a single coil, both coil positive wires must
be connected to the coil.

RPM LIMITERS

The MSD-8 Plus Ignition is equipped with a 2-Step Rev Control. The Ignition will accept two rpm
modules so two different rev limits can be set. One rev limit can be used for over-rev protection while
the second limit can be activated on the starting line for a lower rpm limit to assist in staging and for
consistent holeshots. When 12 volts are applied
to the 2-Step terminal (2’S’), Module 1 is active.
Module 2 is active when there is no 12 volts.

CYLINDER SELECT

This ignition can be used on 2, 4, 6 (even-fire)
or 8-cylinder engines. The ignition is set for
8-cylinder operation. To program the unit for
other engines, remove the one screw that holds
the cover to reveal three wire loops (Figure

1). Cutting a wire loop determines the cylinder
selection.

Cylinders Loops to Cut

8 None
6 One
4 Two
2 Three

Figure 1 Cylinder Programming.

Cut loops

Remove cap

SPARK LED

When the coil fires, current is sensed and this LED will flash. These LEDs confirm that the ignition
has received a trigger signal and that the ignition is working properly. Each time a coil fires, current
is sensed and the corresponding LED will flash. (If the coil is not connected, the LED will not flash.)
When the engine is running, it will appear solid.

M S D   •   W W W . M S D P E R F O R M A N C E . C O M   •   ( 9 1 5 )   8 5 7 - 5 2 0 0   •   F A X   ( 9 1 5 )   8 5 7 - 3 3 4 4

2 INST A L L A TION I N S TRUCT I O N S

GENERAL INFORMATION

BATTERY

An MSD-8 Plus Ignition Control will operate on any negative ground, 12 volt electrical system with a
distributor. The MSD can be used with 16 volt batteries and can withstand a momentary 24 volts in
case of jump starts. The Ignitions will deliver full voltage with a supply of 10-18 volts.
If your application does not use an alternator, allow at least 30 amp/hour for every half hour of
operation. If the engine is cranked with the same battery or other accessories such as an electric fuel
or water pump, the amp/hour rating should be higher.

COILS

The MSD-8 Plus Ignition must be used with an MSD Pro Power Series Coil. The Pro Power HVC, PN
8251, Pro Power HVC II, PN 8261 or for short duration racing, the PN 8201 Pro Power Coil. If you
have any questions concerning coils, contact our Customer Service Department at [phone].

TACHOMETERS

The MSD Ignition features a Tach Output Terminal on the terminal strip. This terminal provides a
trigger signal for tachometers, a shift light or other add-on rpm activated devices. The Tach Output
Terminal produces a 12 volt square wave signal with a 20% duty cycle.

SPARK PLUGS AND WIRES

Spark plug wires are very important to the operation of your ignition system. A good quality, helically
wound wire and proper routing are required to get the best performance
from your ignition, such as the MSD Heli-Core or 8.5mm Super Conductor.

TACH

Note: Solid Core spark plug wires cannot be used with an MSD Ignition.

TERMINAL

A helically, or spiral wound wire must be used. This style wire provides
a good path for the spark to follow while keeping Electro Magnetic
Interference (EMI) to a minimum. Excessive EMI, such as the amount that
solid core wires produce, will interfere with the operation of the MSD and
other electronics on your car.

MOUNTING

The MSD can be mounted in most positions. It can be mounted in the engine compartment as long
as it is away from direct engine heat sources. It is not recommended to mount the unit in an enclosed
area such as the glovebox.
When you find a suitable location to mount the unit, make sure the wires of the ignition reach their
connections. Hold the Ignition in place and mark the location of the mounting holes. Use a 1/4” drill
bit to drill the holes. Install the vibration mounts to the ignition and mount the unit.

Figure 2 Tach Terminal.

M S D   •   W W W . M S D P E R F O R M A N C E . C O M   •   ( 9 1 5 )   8 5 7 - 5 2 0 0   •   F A X   ( 9 1 5 )   8 5 7 - 3 3 4 4

INST A L L A TION I N S TRUCT I O N S 3

Terminal Wire

Function

ORANGE

Connects to the positive (+) terminal of the second coil.This is the only
wire that makes electrical contact with the coil positive terminal.

COIL 2 +

BLACK

Connects to the negative (-) terminal of the second coil. This is the only
wire that makes electrical contact with the coil negative terminal.

COIL 2-

HEAVY
BLACK

This wire connects to a good ground, either at the battery negative (-) terminal
or to the engine.

BAT -

HEAVY
RED

GRAY

BAT +

TACHTACH

2-STEP

IGNITION

Connects to a switched 12 volt source. Such as the ignition key or switch.

RED

WHITE

This wire is used to connect to the points, electronic ignition amplifier output
or to the Yellow wire of an MSD Timing Accessory. When this wire is used,

the Magnetic Pickup connector is not used.

POINTS

VIOLETMAG +

GREENMAG -

DARK
BLUE

This wire connects directly to the battery positive (+) terminal or to a positive

battery junction or the positive side of the starter solenoid. Note: Never
connect to the alternator.

This terminal delivers a 12 volt square wave signal as an output for a
tachometer or devices that require an rpm signal.

When this terminal is connected to 12 volts, RPM module 1 is active. When
there is no 12 volts, RPM module 2 is active.

These wires are routed together in one harness from the Magnetic Pickup
connector. The connector plugs directly into an MSD Distributor or Crank
Trigger. It will also connect to factory magnetic pickups or other aftermarket
pickups (Figure 4). The Violet wire is pos. (+) and the Green is neg. (-).

When these wires are used, the Points Terminal is not.

ORANGECOIL 1 +

BLACKCOIL 1-

Connects to the positive (+) terminal of the coil.This is the only wire that
makes electrical contact with the coil positive terminal.
Connects to the negative (-) terminal of the coil. This is the only wire that
makes electrical contact with the coil negative terminal.

WIRING

GENERAL WIRING INFORMATION

Wire Length: All of the wires of the MSD Ignition may be shortened as
long as quality connectors are used or soldered in place. To lengthen the

wires, use one size bigger gauge wire (10 gauge for the power leads and
16 gauge for the other wires) with the proper connections. All connections
must be soldered and sealed.

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.
The MSD-8 Plus has a ground stud just to the left of the terminal strip. Use this to ground other MSD
accessories (Figure 3).

Coil Connections: When using a single coil, both coil positive terminals must be connected to the

coil. Either connect both orange wires to the coil, or use the supplied jumper to connect the two coil
positive termianls at the terminal strip.

GROUND

Figure 3 Ground Stud.

M S D   •   W W W . M S D P E R F O R M A N C E . C O M   •   ( 9 1 5 )   8 5 7 - 5 2 0 0   •   F A X   ( 9 1 5 )   8 5 7 - 3 3 4 4