MSD 8388 Installation

MSD Pro-Billet Ready-to-Run

Chrysler V8 Distributor

PN 8388; 318, 340, 360, PN 8386; 383, 400

PN 8387; 426, 440

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Important:  Read these instructions before attempting the installation.

Parts Included:

1 - Pro-Billet Distributor
1 - Rotor, PN 8467
1 - Distributor Cap
1 - Advance Kit
1 - O-ring Seal

Note: The PN 8386 and PN 8387 distributors feature HEI style plug wire terminals. You may need to 

change the terminals and boots of your wires. MSD offers a kit, PN 8848, that comes with nine 
HEI style boots and terminals.

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.

1 - Gray Tach Jumper
1 - Parts Bag

Replacement Cap

Distributor PN 8386, PN 8387 - PN 8431
Distributor PN 8388 - PN 8437 or PN 8433

:

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  pl u s  the  centri f u g a l  advance  added  tog e t h e r.  
Example:  10°  Initial + 25° centrifugal  =  35°  Total Timing (When checking Total timing, disconnect 
anc cap the vacuum canister and plug the vacuum line).

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.

RPM LIMIT AND TACHOMETER INFORMATION

Tach Signal:  The Ready-to-Run Distributor features a Gray Tach Output wire which provides a clean signal 

for most tachometers and even some aftermarket fuel injection systems. The signal output 
is a 12 volt square wave, 20° duty cycle.  This wire is also responsible for programming the 
built-in rev limiter.

Rev Limiter: The Ready-to-Run Distributor has a built-in rev limit that can easily be adjusted from 2,000 

rpm to over 10,000 rpm. The default is 10,000 rpm. To set the rev limiter, run the engine to half 
the desired rpm then ground the Gray tach wire (a jumper is supplied) for approximately one 
second. Every time the key is turned to the On position, the tach will display the programmed 
rpm limit. See page 8 for the programming procedure.

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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, 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 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  o f  the  centrifugal  advance  c urve  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  equip ped  with  two  Heavy  Silver  springs 
install ed.    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  tha t  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.

BUSHING SIZE APPROXIMATE
CRANKSHAFT
DEGREES

Red-Smallest - 0.283"  28
Silver - 0.313"  25
Blue - 0.343"  21
Black-Largest - 0.375"  18

Figure 5 Advance Stop Bushing Chart.

Figure 6 Changing the Advance Stop Bushing.

LOCKING OUT THE CENTRIFUGAL
ADVANCE

1.  Remove the cap and rotor.

2.  R e move   th e  a dvan c e   s p ring s ,  w e ight s 
and  the  advance  stop  bushing  from   the

  advance assembly.

3.   Remove the roll-pin from the shaft and slide the 
retaining sleeve down (Figure 7).

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

5.  R ot at e  t h e   s ha ft   18 0 °  a n d   i ns er t  t h e 

advance  stop  bushing  pin  into  the  small 
  hole on the advance plate (Figure 8).

6.  I n st a ll   the   loc k nu t   an d  wash e r  to  th e 

  advance stop bushing pin.

7.  Install the retaining sleeve and roll-pin.

Figure 7 Removing the Retaining Sleeve.

Figure 8 Locking Out the Centrifugal Advance.

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INSTALLATION INSTRUCTIONS 5

OPTIONAL 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 bolts in the 
position of 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 9).

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. It is important to  make  sure 
the pickup plate is parallel with the housing of the 
distributor  (Figure  10).  If  it  is  cocke d  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

CANISTER

SCREWS

Figure 9 Removing the Vacuum Canister.

MAG PICK-UP

PLATE

SNAP

RING

Note: If no  shims   were  r equired,  use  one  beneath 

the washer of the Lock-Out Hold Down Screw.

6.  Aft er  checking  the  reluctor  to  pickup  clearance, 
tighten the Lockout retaining screws and install the 
snap ring.

7.  Install  the  distributor,  rotor  and  cap.  Check  the 
timing when complete.

Note: Do  not  forget  to  plug  the  original  va cuum 

advance hose.

Figure 10  Checking Installation of the Lockout Plate.

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6 INSTALLATION INSTRUCTIONS

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.
Note this position by making a mark (Figure

11).

3.  Place  the  distributor  cap  b ack  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, 
slide the clamp out of the way and lift the 
distributor out of the engine.

6.  Install the supplied O-ring seal in the groove 
on the distributor land.  Apply a thin layer 
of oil to the housing O-ring.

7.  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.

8.  Position and tighten the hold-down clamp onto the distributor.  

9.  Install the rotor and distributor cap. It is recommended to use a drop of Blue Loctite on the distributor 
cap hold down bolts.

10. Install the spark plug wires from the old cap one at a time to ensure correct location.

11. Connect the  supplied wiring harness to the distributor. Route  the wires to their connections as 
shown in Figure 12.

12. Page 8 shows how to set the rev limiter and connect the tachometer.  

Figure 11 Marking the Rotor Location.

        Figure 11 Connecting an MSD Ignition Control.

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INSTALLATION INSTRUCTIONS 7

GRAY TO
TACH INPUT

        Figure 12  Wiring the Ready-to-Run Chrysler Distributor.

GRAY TO
TACH INPUT

Figure 13 Connecting an MSD Ignition Control.

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TACHOMETER INFORMATION

The MSD Ready-to-Run has a Gray wire that provides a 12 volt square wave, 20° duty cycle tachometer 
signal that will trigger most tachometers. It is recommended to connect this lead to your tach’s trigger 
input wire and check its operation. Note that the rpm limiter is extremely accurate and due to the variety 
of tachometers available, there may be differences in the displayed rpm.

PROGRAMMING THE REV LIMIT

A tachometer is required to set the rev limit. The limit is programmed by 
running the engine at half the desired rpm, then momentarily grounding 
the Gray tach output wire from the MSD. A Gray jumper wire is supplied 
to connect to the tach with another tee-splice coming  off to use for 
programming. A switch may also be installed to ease adjustments of 
the limiter (Figure 14). The default rpm limit is 10,000 rpm and the limit 
is adjustable from 2,000 - over 10,000 rpm..

1. Start the engine and bring the rpm to half the desired rev limit (for a 
6,000 rpm limit, raise and hold the rpm to 3,000).

2. While holding the rpm steady, short the Gray tach wire to ground 
for approximately one second. Note that the tach will go to zero 
while grounded.

3. The tach will now display the programmed rev limit amount for two 
seconds. If this value does not register on the tach, repeat the procedure and try a different ground 
source.

4. To confirm the rev limit value, turn the ignition key to the On position (without cranking the engine). The 

rev limit value will be displayed for two seconds on the tachometer.  

OPTIONAL

PROGRAMMING

SWITCH

TO

TACH

Figure 14 Setting the Rev Limiter.

JUMPER GRAY

Note: This rpm confirmation only displays when the Gray wire is being used to trigger the tachometer.

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.msdperformance.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 at [phone]. MSD technicians are available from 7:00 a.m. to 
5:00 p.m. Monday - Friday (mountain time).

Limited Warranty

  M

SD 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. 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. 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 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. Any modifications to this item or if it is used on an application other than what MSD 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 will accept no liability for custom applications.

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© 2012 Autotr onic Con trols Corporation

FRM30249          Revised 01/12        Printed in U.S.A.