MSD 85805 Installation

MSD Ford Billet Distributors

PN 8473: 2.3L, PN 8580: 351C, 351M, 400, 429, 460

PN 8582: 289, 302, PN 8584: 351W

PN 85805: 351W w/Edelbrock Victor Jr. Intake

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Important:  Read these instructions before attempting the installation.

Note: An MSD Ignition is required with this Distributor.

Parts Included:

1 - Billet Distributor
  1 - Rotor
  1 - Distributor Cap

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

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

1 - Advance Kit
1 - Tube of Gear Lubricant
1 - O-Ring

Note: These distributors must be used with an MSD Ignition Control. 

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.

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 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.

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  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  b e 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   •   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