MSD 8423 Installation

MSD Rotor, PN 8423

Fits MSD Cap-A-Dapt, PN 8445 and PN 8441

also, MSD Distributors with Cap PN 8408

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in our monthly 8.5mm Super Conductor Spark Plug Wire give-away! Registering your product
will help if there is ever a warranty issue with your product and helps the MSD R&D team create
new products that you ask for! Go to www.msdperformance.com/registration.

Parts Included:

1 – Rotor, PN 8423
2 – 5/8” Phillips Head Screws

WARNING:  Disconnect the battery during installation. When disconnecting the battery, always
            remove the negative cable first and install it last.

IMPORTANT: There are two different length screws supplied with this rotor. It is important to determine 
which screws are correct for your application due to clearance of the magnetic pickup.

Remove the cap, rotor and the cap spacer and note the rotor screw retainer that is installed on the bottom 
of the advance plate (Figure 1). There are two styles used; one is a Screw Retainer, the other is a Retainer 
with a Nut. The Retainer accepts the shorter 5/8” screw while the Nut version accepts the ¾” screw.

USE 3/4"
SCREW

ROTOR SCREW
RETAINING NUT

2 – 3/4” Phillips Head Screws
2 – Belleville Washers

USE 5/8"

SCREW

ROTOR SCREW

RETAINER

Figure 1 Determining Rotor Screw Length.

Note:  It is recommended to install the rotor and check the clearance 

before reassembling the distributor.

Once the rotor screw length is determined, install the rotor being 
sure the round  and  square aligning  pegs  are lined up  correctly. 
Install the Belleville washers with the dome facing up on the screws 
and tighten the rotor (Figure 2). Install the cap and plug wires.

Figure 2 Washer Installation.

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TECH NOTES

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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.

M S D   •   W W W . M S D P E R F O R M A N C E . C O M   •   ( 9 1 5 )   8 5 7 - 5 2 0 0   •   F A X   ( 9 1 5 )   8 5 7 - 3 3 4 4

© 2012 Autotr onic Controls C orpora tion

FRM28604 Revised 12/11 Printed in U.S.A.