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.
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Page 2
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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Page 3
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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Page 4
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 shaft retaining sleeve
and slide the shaft up.
3. Rotate the shaft 180° and insert the advance stop
bushing pin into the small hole on the advance
plate (Figure 7).
4. Install the locknut and washer to the advance stop
bushing pin. This locks the advance in place.
5. Install the retaining sleeve and its roll-pin.
Figure 6 Changing the Advance Stop Bushing.
Figure 6 Locking Out the Centrifugal Advance.
Figure 7 Locking Out the Advance.
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Page 5
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 new O-ring and apply a liberal
amount of the supplied lubricant to the distributor gear.
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.
Figure 8 Marking the Rotor Location.
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Page 6
6 INSTALLATION INSTRUCTIONS
GREEN
PN 8860
HARNESS
VIOLET
GREEN
VIOLET
FROM
IGNITION KEY
(ORIGINAL COIL WIRE)
IGNITION
KEY
RED
WHITE (NOT USED)
TO 12V
ORANGE
BLACK
+
T
A
C
H
C+
C-
IGN
PTS
M+
M-
GROUND
RPM
7200
HEAVY BLACK
HEAVY RED
+
TO BATTERY
TO BATTERY
+
PRO POWER COIL
HEAVY RED
TACH
OUTPUT
FROM
IGNITION KEY
(ORIGINAL COIL WIRE)
IGNITION KEY
RED
WHITE (NOT USED)
ORANGE
BLACK
TO 12V
HEAVY BLACK
GREEN
PN 8860 HARNESS
VIOLET
+
TO BATTERY
TO BATTERY
+
+
Multiple
Spark
Discharge
PART NO.
AUTOTRONIC CONTROLS CORPORATION
SERIAL NO..
IGNITION
®
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 9 Wiring to an MSD 6-Series Ignition Control.
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Figure 10 Wiring to an MSD 7-Series Ignition Control.
Page 7
INSTALLATION INSTRUCTIONS 7
T
A
C
H
C+
C-
IGN
PTS
M+
M-
HEAVY RED
TO GROUND
NOT USED
WHITE
WHITE
TIMING
CONTROL
SWITCHED 12 VOLTS
FROM IGNITION KEY
YELLOW
RED
RED
BLACK
NOT
USED
ORANGE
HEAVY BLACK
+
GREEN
VIOLET
+
TO BATTERY
TO BATTERY
THRUST COLLAR
PRESS FIRMLY TO
TAKE OUT ALL END
PLAY BEFORE
MEASURING.
4.005” MAX.
3.996” MIN.
Note: MSD 6 and 7 Series Ignitions
share the same color wiring.
Figure 11 Wiring with an MSD 7-Series Ignition and Timing Control.
REPLACING THE DISTRIBUTOR GEAR
To replace the distributor gear on the MSD Distributors, the following steps must be followed.
1. Remove the original spiral pin with a punch and press the original gear off the shaft. Press the new
gear onto the shaft and line up the holes for the spiral pin. Note: The holes may not line up.
2. If the holes line up, measure the distance as shown in the diagram. If the measurement is not correct
or the holes do not line up, a new hole must be drilled. If the measurement is within specifications
and the holes line up, install a new spiral pin.
3. To drill a new hole, turn the gear on the shaft so the gear hole is approximately 90° to the original
shaft hole. Carefully position the gear on the shaft to match the specifications given in the drawing.
Note: Before measuring, push the shaft in to remove all of the end play.
4. When the gear is in the correct position, drill a 0.125” hole through the distributor shaft. Install a
new spiral pin and recheck the measurement.
Note: If the measurement is not within specifications after drilling, a slight correction can be made by
machining the upper face of the thrust collar. Do not remove more than 0.010” or rotor-to-cap
interference may result.
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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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