THEORY OF 6 SERIES IGNITION
The MSD 6 Series Ignitions feature a capacitive discharge ignition design. The majority of stock ignition systems are inductive ignitions. In an inductive ignition, the coil must store
and step up the voltage to maximum strength in between each firing. At higher rpm, since
there is less time to charge the coil to full capacity, the voltage falls short of reaching maximum
energy which results in a loss of power or top end miss.
The MSD Ignition features a capacitor which is quickly charged (within one millisecond)
with 460 – 480 volts and stores it until the ignition is triggered. With the CD design, the
voltage sent to the coil is always at full power even at high rpm.
The MSD 6 Series produces full power multiple sparks for each firing of a plug. The number
of multiple sparks that occur decreases as rpm increases, however the spark series always
lasts for 20° of crankshaft rotation. Above 3,000 rpm there is simply not enough “time” to fire
the spark plug more than once, so there is only one powerful spark.
6AL, 6ALN, 6BTM: These ignitions are equipped with built-in Adjustable Soft Touch Rev
Controls. MSD Rev Limiters are adjustable with plug-in modules which are available in 100
rpm increments. The Soft Touch circuitry provides a smooth and accurate rev limit by
dropping the spark to individual cylinders. The Soft Touch produces a load-free rev limit
that is within 1% of the selected rpm.
1 – MSD 6 Series Ignition1 – 100V/1A Diode
1 – Harness, PN 88604 – Wire Splicers
1 – Harness, PN 88612 – Wire Ties
1 – 18″ Ground Wire1 – Faston Receptacle
1 – White Jumper2 – Faston Straight Terminals
1 – Red Jumper
4 – 45° Faston Terminals 6T, 6TN, 6AL 6ALN, 6BTM, 6-Offroad Only:
4 – #8 x 3/4″ Screws4 – Vibration Mounts and Hardware
2 – 10-32 x 1/2″ Screws
4 – 10-32 Hex Nuts 6AL, 6ALN, 6BTM Only:
6 – #10 Lock Washers4 – RPM Modules, 3,000, 6,000, 7,000, 8,000
An MSD 6 Series 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 9 – 18 volts and will operate with a supply voltage as low as five volts.
If your application does not use an alternator, allow at least 15 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 are used, the amp/hour rating should be higher.
The MSD 6 Series Ignitions can be used with most stock coils and aftermarket coils designed
to replace the stock coils. There are some “race only” coils such as the MSD Pro Power Coil,
PN 8201, that cannot be used with a 6 Series MSD Ignition Control. For more information
on recommended coils, consult the supplied Coil Application Chart or check with the
manufacturer of your coil. If you have any questions concerning coils, contact our Customer
Service Department at (915) 855-7123.
The MSD Ignition features a Tach Output Terminal on the
side of the unit. 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.
Some vehicles with factory tachometers may require a Tach
Adapter to operate with the MSD. For more information on
Tachometers and MSD Tach Adapters, see the Tachometer
Section on page 7.
If your GM vehicle has an inline filter it may cause the tach to
drop to zero on acceleration. If this occurs, bypass the filter.
Due to the fuel injection systems, some foreign vehicles may require a special Tach/Fuel
Injection Adapter to use an MSD Ignition. See pages 7 for wiring and Tach Adapter
Note: Vehicles originally equipped with a CD ignition control cannot use an MSD.
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 Wire.
Note: Solid Core spark plug wires cannot be used with an MSD Ignition.
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