MSD 7222 7AL-2 Ignition Control Installation - Manual (Page 2)

2 INSTALLATION INSTRUCTIONS
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GENERAL INFORMATION
BATTERY
An MSD 7AL-2 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 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, the amp/hour rating should be higher.
COILS
The MSD 7AL-2 Plus Ignition can be used with many stock coils and aftermarket coils designed to
replace the stock coils such as the Blaster line of coils. For short duration racing, like drag racing,
the MSD Pro Power Coil, PN 8201, is recommended. For use on the street or long duration events,
use coil PN 8251 or PN 8261. 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.
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 33% 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 6.
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.
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.
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 the MSD and other
electronics on your car.
Spark Plug Wire Routing: Correct routing of the plug wires is also important to performance. Wires
should be routed away from sharp edges and engine heat sources. If there are two wires that are
next to each other in the engine’s firing order, the wires should be routed away from each other to
avoid inducing a spark into the other wire. For example, in a Chevy V8, the firing order is 1-8-4-3-6- 5-
7-2. The #5 and #7 cylinders are next to each other in the engine and in the firing order. If the voltage
from the #5 wire is induced into #7 detonation could occur and cause engine damage.
To add more heat protection to your plug wires, MSD offers Pro-Heat Guard, PN 3411. This is a glass
woven and silicone coated protective sleeve that you slide over your plug wires. For extra protection
of the spark plug boots, MSD offers Pro-Heat Boot Guard, PN 3412.
TACH
TERMINAL
Figure 2 Tach Terminal.