MSD 8388 Installation

MSD Pro-Billet Ready-to-Run

Chrysler V8 Distributor

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

PN 8387; 426, 440

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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
1 - Advance Kit
1 - O-ring Seal

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.

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.

1 - Gray Tach Jumper
1 - Parts Bag

Replacement Cap

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

:

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  pl u s  the  centri f u g a l  advance  added  tog e t h e r.  
Example:  10°  Initial + 25° centrifugal  =  35°  Total Timing (When checking Total timing, disconnect 
anc 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.

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.

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.

M S D   •   W W W . M S D P E R F O R M A N C E . C O M   •   ( 9 1 5 )   8 5 7 - 5 2 0 0   •   F A X   ( 9 1 5 )   8 5 7 - 3 3 4 4

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, 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  o f  the  centrifugal  advance  c urve  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.

M S D   •   W W W . M S D P E R F O R M A N C E . C O M   •   ( 9 1 5 )   8 5 7 - 5 2 0 0   •   F A X   ( 9 1 5 )   8 5 7 - 3 3 4 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  equip ped  with  two  Heavy  Silver  springs 
install ed.    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  tha t  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   •   W W W . M S D P E R F O R M A N C E . C O M   •   ( 9 1 5 )   8 5 7 - 5 2 0 0   •   F A X   ( 9 1 5 )   8 5 7 - 3 3 4 4