MSD 8572 Installation

MSD Pro-Billet Chevrolet V8

Tach Drive Distributor

PN 8571

with Vacuum Advance, PN 8572

Important:  Read these instructions before attempting the installation.

Note:  An MSD Ignition is required with this Distributor.

Parts Included:

1 - Pro-Billet Distributor
  1 - Rotor, PN 8467
  1 - Distributor Cap, PN 8433
  1 - Wire Retainer
  2 - 1.5" Self Tapping Screws
  2 - 10-32 x 3/4" Socket Head Screws

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

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

Note:  The cap of this 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. A socket style cap is available as PN 8437.

Note:  If the gear is ever replaced, MSD Gear (PN 8531) is required for replacement due to the 

.500" diameter shaft.

1 - Advance Kit
1 - Gasket
1 - Tube of Gear Lubricant
2 - O-Rings
1 - Vacuum Advance Lock-Out Kit
  (PN 8572 Only)
1 - Gear Drive Adapter

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 
the vacuum canister and plug the vacuum source).

Vacuum Advance (PN 8572 Only): 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 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.

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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.

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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.

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

Timing Curve From Factory

Figure 2 The Factory Equipped Curve. 

Figure 3  Spring Combination Chart. 

Figure 4  Advance Curves.

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4 INSTALLATION INSTRUCTIONS

SELECTING THE ADVANCE STOP
BUSHING

Three  different  advance  stop  bushings  are 
supplied  in the  distributor  kit.  The  distributor 
comes  with  a  Blue  (21°)  bushing  already 
installed.  If  a  different  amount  of  centrifugal 
advance  is  desired,  follow  the  next  procedure  
to change the bushings. The  chart  in  Figure 5 
gives the size and approximate degrees for the 
corresponding bushings.

CHANGING THE ADVANCE STOP
BUSHINGS

1.  Remove the distributor cap and rotor.

2.  Remove the locknut and washer on the bottom 
of the advance assembly (Figure 6).

3.  Remove the bushing and install the new one.  
Install the washer and locknut.

BUSHING SIZE APPROXIMATE
CRANKSHAFT
DEGREES

Red-Smallest  28
Silver  25
Blue  21
Black-Largest  18

Figure 5  Advance Stop Bushing Chart.

LOCKING OUT THE CENTRIFUGAL
ADVANCE

1. Remove the advance components including 
the  springs,  weights  and  the  advance  stop 
bushing from the advance assembly.

2. Remove the roll-pin from the drive gear and 
remove the gear from the shaft.

3. Slide the shaft two inches out of the housing.

4. Rotate the shaft 180° and insert the advance 
stop bushing pin into the small hole on the 
advance plate (Figure 7).

5. Install the locknut and washer to the advance 
stop bushing pin. This locks  the advance in 
place.

6. Install the drive gear and roll-pin.

Note: If you want to lock out the vacuum advance 

of the PN 8572 Distributor, see page 6.

Figure 6  Changing the Advance Stop Bushing.

Figure 6  Locking Out the Centrifugal Advance.

Figure 7  Locking Out  the Advance.

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INSTALLATION INSTRUCTIONS 5

INSTALLING THE DISTRIBUTOR

1. Remove the existing distributor cap without 
disconnecting any of  the spark plug wires.

2. With the cap off, crank the engine until the 
rotor is aimed at a fixed point on the engine 
or firewall. Note this position by making a  
mark (Figure 8).

3. Place  the  distributor cap  back  on  and 
note which plug wire the rotor is pointing 
to. MARK THE SPARK PLUG WIRES and 
remove the distributor cap.

4. Disconnect the wiring from the distributor.

5. Loosen the distributor hold down clamp 
and slide the clamp out of the way.

6. Lift the distributor out of the engine.  Note 
that the rotor rotates as you lift the distributor 
out. This is due to the helical cut gear and 
should be taken into consideration when 
installing the new distributor.

7. Install the gasket and apply a liberal amount 
of the supplied lubricant to the distributor 
gear. (The supplied O-rings can only be 
used  if the block has  been modified  as 
shown in Figure 9.)

8. Install the distributor making  sure that the 
rotor comes  to rest pointing at the fixed 
mark. If the distributor will not fully seat with  
the rotor pointing to the  marked position, 
you may need to rotate the oil pump shaft 
until the rotor lines up and the distributor 
fully seats.

9. Position and tighten the hold down clamp 
onto the distributor.

10. Install the distributor cap and spark plug wires 
one at a time to ensure correct location. A 
wire retainer is supplied to secure the wires 
in place. Align the mounting bosses and 
use the supplied 1.5" self-tapping Phillips 
screws to hold the retainer in place.

Figure 8  Marking the Rotor Location.

Figure 9  Modified Block for use with O-Rings.

Installation Option: This Cap  can  also  be 
bolted down to an  MSD Pro-Billet or Billet 
Distributor base with the supplied hardware. 
To accomplish this, the spring clips must be 
cut off (Figure 10).
Note: When  the  cap  is  bolted  down, the

location of the spark plug wires must 
be changed.

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Figure 10  Optional Installation by Bolting Cap Down.

6 INSTALLATION INSTRUCTIONS

MECHANICAL DRIVE

When  using  a  stock  GM  mechanical  drive  tach  the  supplied  square  tach  drive  adapter  must 
be  used.  The  gear  drive  comes  pre-lubed  from  the  factory.  When  lubricating  the  tach  cable, 
it is recommended to lube the gear set. The backlash is set at the factory,  however  it  can  be 
adjusted.

VACUUM ADVANCE LOCKOUT

If you do not want to use the vacuum advance 
canister  of  the PN  8572,  MSD  has  supplied  a 
lockout mechanism.

1.  Remove  the two Allen head screws that hold 
the advance canister (Figure 11).

2.  Remove the snap ring that holds the magnetic 
pickup assembly in place.

3.  Gently lift up on the mag pickup plate and slide 
the vacuum canister out.

4.  Install the Lockout Plate in place of the canister. 
Install the two retaining screws.

5.  Install the supplied screw and washer through 
the Lockout and tighten.

6. It  is  important  to  make  sure  the pickup  plate 
is  parallel  with  the  housing  of  the  distributor 
(Figure 12). If it is cocked or slanted, the paddles 
of the reluctor may contact the pickup. Check 
the clearance by rotating the distributor shaft. 
If necessary, use the supplied shims under the 
Lockout hold-down  to  correctly  position the 
pickup plate.

Note: If no shims were required, use one beneath 

the  washer  of  the  Lock-Out  Hold  Down 
Screw.

ReluctoR

Paddles

snaP

Ring

Figure 11   Removing the Vacuum Canister.

Mag PickuP

Plate

canisteR

scRews

Note: Do not forget to plug the original vacuum 

advance hose.

Figure 12  Checking Installation of the Lockout Plate.

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INSTALLATION INSTRUCTIONS 7

WARNING: High voltage is present on the coil terminals. Do not touch the terminals or 

coil tower when the engine is cranking or running. 

        Figure 13  Wiring to an MSD 6-Series Ignition Control.

        Figure 14  Wiring to an MSD 7-Series Ignition Control.

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Note: MSD  6  and  7  Series  Ignitions 

share the same color wiring.

        Figure 15  Wiring with an MSD 7-Series Ignition and Timing Control.

Service

  In case of malfunction, this MSD component will be repaired free of charge according to the terms of the warranty. 

When returning MSD components for warranty service, Proof of Purchase must be supplied for verification. After 
the warranty period has expired, repair service is based on a minimum and maximum fee.

All returns must have a Return Material Authorization (RMA) number issued  to  them before 

being returned.  To  obtain  an  RMA  number please contact  MSD  Customer Service at 1 (888)  MSD-7859 or 
visit  our  website  at  www.msdignition.com/rma  to  automatically  obtain  a  number  and  shipping  information.

When returning the unit for repair, leave all wires at the length in which you have them installed. Be sure to include 
a detailed account of any problems experienced, and what components and accessories are installed on the vehicle. 
The repaired unit will be returned as soon as possible using Ground shipping methods (ground shipping is covered 
by warranty). For more information, call MSD Ignition at [phone]. MSD technicians are available from 7:00 
a.m. to 6:00 p.m. Monday - Friday (mountain time).

Limited Warranty

  M

SD IGNITION warrants this product to be free from defects in material and workmanship under its intended normal 
use*, when properly installed and purchased from an authorized MSD dealer, for a period of one year from the date 
of the original purchase. This warranty is void for any products purchased through auction websites. If found to be 
defective as mentioned above, it will be repaired or replaced at the option of MSD Ignition. Any item that is covered 
under this warranty will be returned free of charge using Ground shipping methods. 
  This shall constitute the sole remedy of the purchaser and the sole liability of MSD Ignition. To the extent permitted 
by law, the foregoing is exclusive and in lieu of all other warranties or representation whether expressed or implied, 
including any implied warranty of merchantability or fitness. In no event shall MSD Ignition or its suppliers be liable 
for special or consequential damages.
  *Intended normal use means that this item is being used as was originally intended and for the original application 
as sold by MSD Ignition. Any modifications to this item or if it is used on an application other than what MSD Ignition 
markets the product, the warranty will be void. It is the sole responsibility of the customer to determine that this item 
will work for the application they are intending. MSD Ignition will accept no liability for custom applications.

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© 2009 Aut otronic C ontrols Co rporatio n

FRM28723          Revised 04/09        Printed in U.S.A.