MSD 6520 Digital 6-Plus Ignition Control Installation - Manual (Page 3)

INSTALLATION INSTRUCTIONS 3
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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 Heli-
Core or 8.5mm Super Conductor Wire. Helically wound wires provide 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. Solid Core spark plug wires cannot
be used with an MSD Ignition.
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 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.
These examples are just starting points to get you going in
the right direction. Every application is different and should
be tested and tuned.
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 screen over the hole to act as a filter.
MOUNTING
The MSD 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. Also be sure that the program dials can be accessed. Hold the Ignition in place and mark the
location of the mounting holes. Use an 1/8” bit to drill the holes or, if using the supplied vibration mounts,
use a 3/16” bit and mount the ignition.
Compression Spark Plug Gap
Up to 10.5:1:
0.050" - 0.060"
10.5:1 - 13.0:1: 0.040" - 0.050"
Above 13.0:1: 0.035" - 0.045"