MSD 8523 Installation
MSD Pro-Billet Ready-to-Run
AMC V8 Distributor
PN 8523
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Important: Read these instructions before attempting the installation.
Parts Included:
1 - Pro-Billet Distributor
1 - Rotor, PN 8467
1 - Distributor Cap, PN 8433
1 - Advance Kit
Note: The terminals of the Ready-to-Run AMC Distributor requires spark plug style terminals. You may
need to change the terminals and boots of your wires. MSD offers two kits, PN 8849 or PN 8848 that
are supplied with nine boots and terminals.
1 - Gasket
1 - Vacuum Advance Lock-Out Kit
1 - Tube of Gear Lubricant
1 - Wiring Harness
1 - Gray Tach Jumper
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 cap
the vacuum canister and plug the vacuum line.)
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.
Note: MSD Distributors are supplied with the heavy (slow) advance springs and the 21° stop bushing
installed. This is to prevent detonation in certain applications. Review the information on pages
2-3 to determine the best advance curve for your application.
RPM LIMIT AND TACHOMETER INFORMATION
Tach Signal: The Ready-to-Run Distributor features a Gray Tach Output wire which provides a clean signal
for most tachometers and even some aftermarket fuel injection systems. The signal output
is a 12 volt square wave, 20° duty cycle. This wire is also responsible for programming the
built-in rev limiter.
M S D I G N I T I O N • W W W. M S D I G NIT I O N . C OM • ( 9 15 ) 8 5 7 - 520 0 • FA X ( 9 1 5 ) 8 5 7-3 34 4
2 INSTALLATION INSTRUCTIONS
Rev Limiter: The Ready-to-Run Distributor has a built-in rev limit that can easily be adjusted from 2,000
rpm to over 10,000 rpm. The default is 10,000 rpm. To set the rev limiter, run the engine to half
the desired rpm then ground the Gray Tach wire (a jumper is supplied) for approximately one
second. Every time the key is turned to the On position, the tach will display the programmed
rpm limit. See page 8 for the programming procedure.
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 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, 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
• Useasmuchinitialadvanceaspossiblewithoutencounteringexcessivestarterload.
• Startthecentrifugaladvancejustabovetheidlerpm.
• The starting point of the centrifugal advance curve is controlled by the installed length and
tension of the spring.
• Howquicklythecentrifugaladvance(slope)comesiniscontrolledbythespringstiffness.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.
M S D I G N I T I O N • W W W. M S D I G NIT I O N . C OM • ( 9 15 ) 8 5 7 - 520 0 • FA X ( 9 1 5 ) 8 5 7-3 34 4
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.
M S D I G N I T I O N • W W W. M S D I G NIT I O N . C OM • ( 9 15 ) 8 5 7 - 520 0 • FA X ( 9 1 5 ) 8 5 7-3 34 4
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