MSD 84111 Installation

MSD Extreme HEI Cap

10-14 x .750
SCREWS

PN 84111

Parts Included In This Kit

1 - PN 84111, MSD HEI Cap
1 - Factory Rotor Bushing
1 - Low Resistance Rotor Bushing, PN 8412
1 - Insulator

This cap is supplied with a stock GM rotor bushing as
well as an MSD Low Resistance Bushing, PN 8412, which
only has 1 - 3 ohms. The Rotor Bushings used in GM
HEI Distributors are made from high resistance carbon
to help suppress radio frequency interference. However,
when the increased voltage and spark energy of an MSD
Ignition Control is added, this high resistance may build
up excessive heat which may damage the cap or rotor.

The Low Resistance Bushing allows the secondary
voltage to be transferred from the cap to the rotor without
excessive heat build up. The stock bushing is black with
a bronze tip while the Low Resistance Bushing is solid
bronze.

1 - Extreme Coil Cover, PN 84022
3 - 10-14 x .750 Screws

Stock HEI or a Performance Coil: It is recommended
to use the Stock Rotor Bushing in stock applications.
The higher resistance reduces the chance of excessive
Electro Magnetic Interference, or radio noise. If you
have only added a performance coil, use this Bushing
as well.

MSD 6A Series Ignitions: GM used a variety of Rotor
Bushings with a large variance in resistance and in
most cases with a 6 Series Ignition, the Low Resistance
Bushing is not required. In applications where the engine
will be running at high rpm for long amounts of time, it is
recommended to use. If you experience any problems
within your cap and rotor, install the PN 8412.

MSD Digital Ignitions and 7 Series Ignitions: The Low
Resistance Bushing is required.

Note: The MSD Pro-Billet HEI Distributor, PN 8365, is
supplied with the Low Resistance Bushing.

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 Corporatio n

FRM28511 Revised 12/11 Printed in U.S.A.