MSD Ignition 8485 Operation and maintenance manual

AUTOTRONIC CONTROLS CORPORATION • 1490 HENRY BRENNAN DR., EL PASO, TEXAS 79936 • [phone] • FAX [phone]
Installation Instructions
MSD Billet VW Distributor
PN 8485
Important: Read these Instructions before attempting the installation.
Contents
Timing Functions
Choosing an Advance Curve
Setting or Locking Out the Centrifugal Advance
Installing the Distributor
Wiring the Distributor
Parts Included In This Kit
1 Billet Distributor
2 #10 Disc Washers
3 Advance Stops
1 Retaining Nut
7 Shims
1 Clamp Stud
4 Advance Springs
1 Hold Down Bracket
2 O-Rings
TIMING FUNCTIONS
Before continuing with the installation, here are a few definitions you should be
aware of:
Initial Timing: This is the base timing of the engine before centrifugal advance
begins.
Centrifugal Advance: The centrifugal advance mechanism is made up of weights,
springs, advance cam, 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.
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.

2 INSTALLATION INSTRUCTIONS
AUTOTRONIC CONTROLS CORPORATION • 1490 HENRY BRENNAN DR., EL PASO, TEXAS 79936 • [phone] • FAX [phone]
FACTOR Advance Timing Retard Timing
For For
Cylinder Pressure Low High
RPM High Low
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 11.5:1compression, 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 2 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 or engine kick-back.
• 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.

INSTALLATION INSTRUCTIONS 3
AUTOTRONIC CONTROLS CORPORATION • 1490 HENRY BRENNAN DR., EL PASO, TEXAS 79936 • [phone] • FAX [phone]
Figure 2 Advance Curves.
CENTRIFUGAL ADVANCE CURVE
The centrifugal advance mechanism is made up of weights, springs, an advance
cam and the advance stop bushing. The distributor can be used in a wide selection
of applications by changing only the springs and the advance stop bushing. There
is no need to change the weights or advance cam.
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. 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.

4 INSTALLATION INSTRUCTIONS
AUTOTRONIC CONTROLS CORPORATION • 1490 HENRY BRENNAN DR., EL PASO, TEXAS 79936 • [phone] • FAX [phone]
SPRING COMBINATION RATE OF ADVANCE GRAPH NO. (Page 3)
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.
INSTALLING THE ADVANCE SPRINGS
1. Remove the distributor cap and rotor.
2. Using long needle nose pliers, remove the springs from the spring posts.
3. Install the new springs using the pliers and install the rotor and cap.
SELECTING THE ADVANCE STOP BUSHING
Three different advance stop bushings are supplied in the distributor kit. The
distributor comes with a Blue (10.5 ) bushing already installed. If a different amount
of centrifugal advance is desired, follow the next procedure to change the bushings.
The chart in Figure 4 gives the size and approximate degrees for the corresponding
bushings.
BUSHING SIZE APPROXIMATE CRANKSHAFT
DEGREES
Red-Smallest 28
Silver 25
Blue 21
Black-Largest 18
Figure 4 Advance Stop Bushing Chart.

INSTALLATION INSTRUCTIONS 5
AUTOTRONIC CONTROLS CORPORATION • 1490 HENRY BRENNAN DR., EL PASO, TEXAS 79936 • [phone] • FAX [phone]
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 5).
3. Remove the bushing and install
the new one. Install the washer
and locknut.
Figure 5 Changing the Advance Stop Bushing.
LOCKING OUT THE CENTRIFUGAL ADVANCE
1. Remove the roll-pin from the
drive gear and remove the gear
from the shaft.
2. Remove the advance springs,
weights and the advance stop
bushing from the advance
assembly.
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 6).
5. Install the locknut and washer
to the advance stop bushing
pin.
6. Install the drive gear and roll-
pin.
Figure 6 Locking Out the Centrifugal Advance.

6 INSTALLATION INSTRUCTIONS
AUTOTRONIC CONTROLS CORPORATION • 1490 HENRY BRENNAN DR., EL PASO, TEXAS 79936 • [phone] • FAX [phone]
INSTALLING THE DISTRIBUTOR
1. Set the No. 1 cylinder toTDC under compression.
2. Remove the distributor cap. Note the position of the rotor and which spark plug
terminal it is pointing to. Mark the plug wire and the position of the rotor.
3. Remove the distributor
and the distributor
shaft spring.
3. Make sure the position
of thedistributor
driveshaft slot is
perpendicular to the
case seam (Figure 7).
If not, move it to the
proper position.
Figure 7 Distributor Driveshaft Position.
4. Remove the original clamp stud and install the supplied longer stud at least 1/2"
into the case. Place the supplied spacer over the stud.
5. Install the collar and clamp to the distributor and snug the bolts (Figure 8).
Install the distributor into the engine making sure that it bottoms out on the
driveshaft.
6. Screw the nut onto the clamp stud
and finger tighten. Locate the
supplied shims and set one
0.010" shim aside.
7. With the remaining shims, make
a stack that fits the gap between
the clamp and the distributor
housing (Figure 8). It is
recommended to use a shim
stack that is slightly thicker than
the gap up to 0.005" however, it
may be 0.002" thinner.
8. Remove the distributor then
remove the clamp and collar. Add
the one 0.010" shim that you set
aside to the shim stack and place
them on the distributor.
9. Install the clamp and collar so the
shims are sandwhiched between
the housing and the clamp.
Tighten the clamp and install the
two o-ring seals or use the original seal if it’s in good shape.
10.Install the distributor shaft spring and the distributor. Make sure the rotor is
pointing to the number one terminal of the distributor cap.
11.Install the cap and spark plug wires. If you are using the original spark plug
wires, the terminals and boots must be replaced with MSD 90° boots and
terminals, PN 8850. MSD offers a set of custom length Heli-Core Wires for VW,
PN 3193.
Figure 8 Measuring the Required Distributor Shims.

INSTALLATION INSTRUCTIONS 7
AUTOTRONIC CONTROLS CORPORATION • 1490 HENRY BRENNAN DR., EL PASO, TEXAS 79936 • [phone] • FAX [phone]
WIRING
The MSD Billet VW Distributor must be used with and MSD Ignition Control. Figure
9 shows the correct wiring of the ignition system.
Figure 9 Wiring the Billet Distributor.
TECH NOTES
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AUTOTRONIC CONTROLS CORPORATION • 1490 HENRY BRENNAN DR., EL PASO, TEXAS 79936 • [phone] • FAX [phone]
Limited Warranty
A utotronic Controls Corporation warrants MSD Ignition products to be free from defects in material
and workmanship under normal use and if properly installed for a period of one year from date of
purchase. If found to be defective as mentioned above, it will be replaced or repaired if returned prepaid
along with proof of date of purchase. This shall constitute the sole remedy of the purchaser and the sole
liability of Autotronic Controls Corporation. To the extent permitted by law, the foregoing is exclusive
and in lieu of all other warranties or representations whether expressed or implied, including any implied
warranty of merchantability or fitness. In no event shall Autotronic Controls Corporation be liable for
special or consequential damages.
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 service, Proof of Purchase must be supplied for
warranty verification. After the warranty period has expired, repair service is charged based on a minimum
and maximum charge.
Send the unit prepaid with proof of purchase to the attention of: Customer Service Department,
Autotronic Controls Corporation, 1490 Henry Brennan Drive, El Paso, Texas 79936.
When returning the unit for repair, leave all wires at the length in which you have them installed.
Cutting wires close to the unit will void your warranty. 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 after receipt, COD for any charges. For more
information, call the MSD Customer Service Line [phone]. MSD technicians are available from
8:00 a.m. to 5:00 p.m. Monday - Friday (mountain time).
FRM11992 REVISED 01/95 PRINTED IN U.S.A.
TECH NOTES
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