MSD 8420 Installation

MSD Cap-A-Dapt

PN 8420

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Parts Included:

1 – Adapter Base, PN 8446
1 – Rotor (two pieces), PN 8421
1 – Cap – PN 8408

INSTALLATION

1. Leave the spark plug wires in place and remove the
distributor cap.

2. Before removing the rotor, position it in a way
that its location can be noted. Mark the position
of the rotor tip then remove the rotor (Figure 1).

3. Install the Adapter Base onto the distributor making sure the
key way is aligned properly. Push and rotate the retaining
spring clips until they clamp to the distributor housing.

2 – 5/8” Rotor Screws
2 – 3/4” Rotor Screws
2 – Belleville Washers

4. Before installing the rotor base, determine which length
rotor screws are needed for your distributor. Figure 2
shows the two different rotor screw retainers offered

Figure 1 Marking the Position of

the Rotor Tip.

on different MSD distributors.

>

ROTOR SCREW

RETAINER

USE 5/8" SCREW

Figure 2 Determining Rotor Screw Length.

>

ROTOR SCREW

RETAINING NUT

USE 3/4" SCREW

5. Install the Rotor Base with the correct length screws and Belleville washers to the advance plate.
Install the rotor next and its tip should be pointing to the same mark you made in step 2.

6. Install the distributor cap.

7. Transfer the plug wires one at a time in the proper order from the original distributor cap.

M S D   •   W W W . M S D P ER F O R M A N C E . C O M   •   ( 9 1 5 )   8 5 7 - 5 20 0   •   F A X   ( 9 1 5 )   8 5 7 -3 3 4 4

Figure 3 Installing the Cap-A-Dapt.

Note: If you are swapping from a socket style distributor cap to the Cap-A-Dapt you will need new spark

plug terminals and boots. The correct boots and terminals are sold in a set as PN 8850.

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 ER F O R M A N C E . C O M   •   ( 9 1 5 )   8 5 7 - 5 20 0   •   F A X   ( 9 1 5 )   8 5 7 -3 3 4 4

© 2012 Autotr onic Co ntrol s Corporation

FRM29169 Revised 02/12 Printed in U.S.A.