Msd ignition PN 8388, PN318, PN340, PN360, PN 8386 Installation instructions

MSD Pro-Billet Ready-to-Run

Chrysler V8 Distributor

PN 8388; 318, 340, 360, PN 8386; 383, 400

PN 8387; 426, 440

Important: Read these Instructions before attempting the installation.

Parts Included:

1 - Pro-Billet Distributor
1 - Rotor, PN 8467
1 - Distributor Cap
1 - Advance Kit
1 - O-ring Seal
1 - Parts Bag

Note: The PN 8386 and PN 8387 distributors feature HEI style plug wire terminals. You may
need to change the terminals and boots of your wires. MSD offers a kit, PN 8848, that comes
with nine HEI style boots and terminals.

Replacement Cap

Distributor PN 8386, PN 8387 - PN 8431
Distributor PN 8388 - PN 8437 or PN 8433

:

TIMING FUNCTIONS

Before continuing with the installation, here are a few definitions you should be aware of:

Initial Timing: This is the base timing (also referred to as idle timing) of the engine before the
centrifugal advance begins.

Centrifugal Advance: The centrifugal (or mechanical) advance mechanism is made up of weights,
springs, advance cams, and an advance stop bushing. The amount and rate of advance that
your distributor is capable of is determined by the centrifugal timing. If you ever wish to lock out
the centrifugal advance, refer to the centrifugal advance section.

Total Timing: This is the total of the initial timing plus the centrifugal advance added together.
Example: 10° Initial + 25° centrifugal = 35° Total Timing. (When checking Total timing, disconnect
and plug the vacuum advance.)

Vacuum Advance: The vacuum advance will advance the timing up to 10° during partial throttle
driving (with 15 lbs of vacuum). The vacuum line should be routed to a ported vacuum outlet
above the throttle plates.

AUTOTRONIC CONTROLS CORPORATION • 1490 HENRY BRENNAN DR., EL PASO, TEXAS 79936 • [phone] • FAX [phone]

2 INSTALLATION INSTRUCTIONS

CHOOSING AN ADVANCE CURVE

The function of the advance curve is to match the ignition timing to the burning rate of the fuel
and speed (rpm) of the engine. Any factor that changes the burning rate of the fuel or the engine
speed can cause a need for an ignition timing change. Figure 1 shows some of the factors that
will affect engine timing.

FACTOR Advance Timing Retard Timing

For For

Cylinder Pressure Low High
RPM High Low
Vacuum High Low
Energy of Ignition Low High
Fuel Octane High Low
Mixture (Air/Fuel) Rich Lean
Temperature Cool Hot
Combustion Chamber Shape Open Compact
Spark Plug Location Offset Center
Combustion Turbulence Low High
Load Light Heavy

Figure 1 Ignition Timing Factors.

As you can see from the chart, most factors will change throughout the range of the engine
operation. The timing mechanism of the distributor must make timing changes based on these
factors.

Example: An engine has 11:1 compression, a high energy ignition and turns 5,500 rpm. With
the specifications given, you will have to retard the timing for the high compression, low rpm
and high energy ignition. By comparing the engine’s specifications against the chart, a usable
timing guideline can be found. Engines with a combination of items from both columns will
require a timing that is set in the mid range.

Obviously a full technical explanation of correct ignition timing would be very complicated. The
best way to arrive at a suitable ignition curve for your engine is to use the Ignition Timing Factors
Chart as a guide and compare it to the Advance Graphs in Figure 4 until a suitable curve is found.
When selecting your advance curve, use detonation (engine ping) as an indicator of too much
advance, and a decrease in power as an indicator of too little advance.

TIPS ON SELECTING AN ADVANCE CURVE

• Use as much initial advance as possible without encountering excessive starter load.

• Start the centrifugal advance just above the idle rpm.

• The starting point of the centrifugal advance curve is controlled by the installed length and
tension of the spring.

• How quickly the centrifugal advance (slope) comes in is controlled by the spring stiffness. The
stiffer the spring, the slower the advance curve.

• The amount of advance is controlled by the advance bushing. The bigger the bushing, the
smaller the amount of advance.

AUTOTRONIC CONTROLS CORPORATION • 1490 HENRY BRENNAN DR., EL PASO, TEXAS 79936 • [phone] • FAX [phone]

INSTALLATION INSTRUCTIONS 3

CENTRIFUGAL ADVANCE CURVE

SELECTING THE ADVANCE SPRINGS

The rate, or how quick the advance comes in is determined by the type of springs which are
installed on the distributor. The MSD distributors are equipped with two Heavy Silver springs
installed. These will give you the slowest advance curve possible. The parts kit contains two
additional sets of springs which can be used to match the advance curve to your particular
application. Refer to the Spring Combination Chart (Figure 3) for combinations that can be
achieved.

To change the springs, remove the cap and rotor and use needlenose pliers to remove the springs.
Be sure the new springs seat in the groove on the pin.

Timing Curve From Factory

SPRING COMBINATION RATE OF ADVANCE FIGURE 4 (Page 3)

2- Heavy Silver SLOWEST A
1- Heavy Silver B
1- Light Blue
1-Heavy Silver C
1-Light Silver
2- Light Blue D
1- Light Silver E
1- Light Blue
2- Light Silver FASTEST F

Figure 2 The Factory Equipped Curve. Figure 3 Spring Combination Chart.

Figure 4 Advance Curves.

AUTOTRONIC CONTROLS CORPORATION • 1490 HENRY BRENNAN DR., EL PASO, TEXAS 79936 • [phone] • FAX [phone]