MSD 8353 Installation

MSD Pro-Billet Front Mount

Ford Flathead Distributor

2-Bolt, 1942-1948, PN 8351
3-Bolt, 1932-1941, PN 8353

Important:

Parts Included:

1 - Pro-Billet Distributor
1 - Rotor
1 - Distributor Cap, PN 8541
2 - 10-32 x 3/4" Socket Head Screws
1 - Advance Kit

WARNING: Before installing the MSD Distributor, disconnect the battery cables. When

Note: The terminals of this Distributor require spark plug style terminals. You may need to change

Note: The 2 and 3-bolt front covers of the Flathead are interchangeable but if a stock type

Note: Contact MSD for ordering information when the rotor needs to be replaced.

Read these Instructions before attempting the installation.

disconnecting the battery cables, always remove the Negative (-) cable
first and install it last.

the terminals and boots of your wires. MSD offers two kits, PN 8849 or PN 8848 that are
supplied with nine boots and terminals.

camshaft is used with a different cover, an adapter/spacer may be required. These are
available at most Flathead engine shops.

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.

Note: MSD Distributors are supplied with the heavy (slow) advance springs installed. This is to

prevent detonation in certain applications. Review the information on pages 2-4 to
determine the best advance curve for your application.

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
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 with a high energy ignition. With the specifications
given, you will have to retard the timing for the high compression 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 (Figure 2). 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

Figure 2 The Factory Equipped Curve.

SPRING COMBINATION RATE OF ADVANCE FIGURE 4

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 3 Spring Combination Chart.

Figure 4 Advance Curves.

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