MSD Pro-Billet Ready-to-Run
Chevrolet V8 Distributor Kit
PN 8474
Important: Read these instructions before attempting the installation.
Parts Inclu d ed:
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
1 - Advance Kit
WARNING: Before installing the MSD Ready to Run Distributor, disconnect the battery cables.
When disconnecting the battery cables, always remove the Negative (-) cable first
and install it last.
Note: The terminals of this Distributor Cap require 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 - 3-Pin Harness
1 - Gasket
1 - Tube of Gear Lubricant
2 - O-Rings
1 - Vacuum Advance Lockout Kit
1 - Coil Wire
1 - Blaster SS Coil, PN 8207
Note: If the gear is ever replaced, MSD Gear (PN 8531) is required for replacement due to the .500"
diameter shaft.
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: 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, a high energy ignition and turns 5,500 rpm. 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.
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.
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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.
LOCKING OUT THE CENTRIFUGAL
ADVANCE
1. Remove the advance 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.
6. Install the drive gear and roll-pin.
BUSHING SIZE APPROXIMATE
CRANKSHAFT
DEGREES
Red-Smallest 28
Silver 25
Blue 21
Black-Largest 18
Figure 5 Advance Stop Bushing Chart.
Figure 6 Changing the Advance Stop Bushing.
Note: If you want to lock out the vacuum advance,
see page 7.
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 p lace. Align the
mounting bosses and use the supplied
1.5" self-tapping Phillips screws to hold the
retainer in place.
Figure 9 Modified Block for use with O-Rings.
Figure 8 Marking the Rotor Location.
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6 INSTALLATION INSTRUCTIONS
IG
N
ITIO
N
TM
Multiple
Spark
Discharge
PART NO.
AUTOTRONIC CONTROLS CORPORATION
SERIAL NO..
TACH OUTPUT
HEAVY BLACK
HEAVY RED
ORANGE
WHITE
RED
BLACK
TO GROUND
TO 12V
TO GROUND
MAGNETIC PICKUP
NOT USED
TO BATTERY
IGNITION KEY
RE
D
ORANGE
RED
BLACK
+
BLASTER SS COIL
PN 8207
ORANGE
BLACK
+
ORANGE
RED
BLACK
ORANGE
RED
BLACK
TO GROUND
TO 12V
IGNITION KEY
BLASTER SS COIL
PN 8207
+
Red
ORange
Black
tO cOil pOsitive +
tO cOil negative
tO engine gROund
-
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Figure 10 Wiring the Ready-to-Run Chevrolet Distributor.
nOte: the Ready-t O-R un distRiB utO Rs dO nOt
Figure 11 Connecting an MSD Ignition Control to the Ready-to-Run Distributor.
RequiRe an Msd ignitiOn, thOugh they can
Be used with One.
INSTALLATION INSTRUCTIONS 7
VACUUM ADVANCE LOCKOUT
If you do not want to use the vacuum advance
canister of the MSD Distributor, MSD has supplied the
distributor with a lockout mechanism. The Lockout
assembly replaces the vacuum canister and will hold
the pickup assembly firmly in place. The installation
is easiest with the distributor out of the engine.
1. Remove the two Allen head screws that hold the
advance canister (Figure 12).
2. Remove the snap ring that holds the magnetic
pickup assembly in place. This is easy to do with
a set of snap ring pliers by straddling one of the
reluctor paddles.
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 13). 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.
ReluctOR
paddles
snap
Ring
Figure 12 Removing the Vacuum Canister.
Mag pickup
plate
canisteR
scRews
Note: If no shims were required, use one beneath the
washer of the Lockout Hold Down Screw.
7. After checking the reluctor to pickup clearance,
tighten the Lockout retaining screws and install
the snap ring.
8. Install the distributor, rotor and cap. Check the
timing when complete.
Note: Do not forget to plug the original vacuum
advance hose.
Figure 13 Checking Installation of the Lockout Plate.
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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 14).
Note: When the cap is bolted down, the location of the spark plug wires must be changed.
Figure 14 Optional Installation by Bolting the Cap Down.
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 (915) 855-7123. 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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© 2008 Aut otronic Con trols Corpo ration
FRM29165 Revised 01/08 Printed in U.S.A.
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