MSD 7720 Power Grid System - Ignition Control Only Installation - Manual (Page 2)

2 INSTALLATION INSTRUCTIONS
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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 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.
Spark Plugs: Choosing the correct spark plug design and heat range is important when trying to get
the best performance possible. Since there are so many engine combinations and manufacturers,
MSD does not recommend which plug or gap is exactly right for your application.
It is recommended to follow the engine builder or manufacturer’s specification for spark plugs. With
that, you can then experiment with the plug gap to obtain the
best performance. The gap of the plugs can be opened in 0.005”
increments, then tested until the best performance is obtained.
MSD judges the plug gap by compression and components:
Note: A larger plug gap taxes the cap, rotor and spark plug
wires. Always inspect the cap and rotor to make sure
they are in good condition.
MISCELLANEOUS INFORMATION
Sealing: Do not attempt to seal the MSD. All of the circuits of an MSD receive a thick conformal
coating of Humi-Seal. This sealant protects the electronics from moisture. If you were to seal the
unit, any moisture or water that may seep in through the wiring grommets will not be able to drain
and may result in corrosion.
Welding: If you are welding on your vehicle, to avoid the chance of damage, always disconnect both
heavy power cables of the MSD. (You should also disconnect the tach ground wire too).
Distributor Cap and Rotor: It is recommended to install a new distributor cap and rotor when installing
the MSD Ignition Control. The cap should be clean inside and out especially the terminals and rotor tip.
On vehicles with smaller caps, it is possible for the air inside the cap to become electrically charged
causing crossfire which can result in misfire. This can be prevented by drilling a couple vent holes
in the cap. The holes should be placed between the terminals, at rotor height and face away from
the intake. If your environment demands it, place a small piece of non-metallic screen over the hole
to act as a filter.