MSD 83647 Installation

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MSD HEAT Digital HEI Module

PN 83647

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This Module is a performance replacement for GM’s 4-Pin HEI Module. It features a programmable rev limiter for overrev protection. The Module will mount in a stock HEI housing (by removing the original condenser assembly) or in MSD’s Pro-Billet HEI Distributor, PN 8365. A GM Coil can be used or for maximum performance, use MSD’s HEI Coil, PN 8225.

Parts Included:

1 - HEI Module, PN 83647 1 - Tube of Heat Sink Compound

Note: A tachometer is required to program the rev limit.

INSTALLATION

1. Mark the location of the spark plug wires on the cap prior to removal.

2. Remove the cap, rotor, module and condenser (if equipped) from the original distributor.

3. Apply a liberal coat of the Heat Sink Compound to the aluminum base of the Module.

4. Route the wiring harness out of the housing and position the short Black wire to ground with one of the mounting screws (Figure 1).

5. Position the module in the distributor then locate the two screws and star washers to secure the module (Figure 1).

6. Reinstall the rotor and cap.

REV LIMIT

BYPASS JUMPER

1 - Gray Tach Wire 2 - Mounting Screws and Star Washers 1 - Low Resistance Rotor Bushing, PN 8412

SCREWS AND

STAR WASHERS

CONNECT SHORT

BLACK WIRE

TO GROUND

CONNECTOR

CAP

DIGITAL

HEI MODULE

APPLY

HEAT SINK

COMPOUND

DISTRIBUTOR

HOUSING

TO TACH

GRAY TACH OUTPUT

USE TO PROGRAM TACH

Figure 1 Installing the Module.

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2 INSTALLATION INSTRUCTIONS

7. Connect the HEI Module harness to the Distributor Cap followed by the 12 volt (BAT) wire. This wire should be at least 14-gauge (Figure 2).

8. Connect the long black wire to the engine block for a solid ground.

9. See the next page for tachometer and rev limit programming.

10. It is recommended to install the supplied low resistance rotor bushing. This improves the spark transfer from the coil to the rotor tip. Remove the coil cover and coil. Replace the rotor bushing.

GRAY

TO TACH

OUTPUT

LONG BLACK

TO ENGINE

GROUND

Figure 2 Connecting the Module and Tach Lead.

TACHOMETER INFORMATION

The HEAT Digital HEI Module has a Gray wire that provides a 12 volt square wave, 20° 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. If the tach requires a higher voltage signal, connect its input wire to the Tach terminal on the HEI Cap (Coil-/Tach). Note that the rpm limiter is extremely accurate and due to the variety of tachometers available, there may be differences in the displayed rpm.

No Rev Limit: To disable the rev limit function, cut and remove the jumper shown in Figure 3.

JUMPER

Figure 3 Disable the Rev Limit.

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INSTALLATION INSTRUCTIONS 3

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 4). The default rpm limit is 10,000 rpm.

OPTIONAL

PROGRAMMING

SWITCH

1. Start the engine and bring the rpm to half the desired

rev limit (for a 6,000 rpm limit, raise the rpm to 3,000).

2. While holding the rpm steady, short the Gray tach wire

TACH

GRAY

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

Figure 4

on the tach, repeat the procedure and try a different ground source.

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

tachometer.

REV LIMITER VERIFICATION

The MSD HEAT HEI Module has an optional built-in Rev Limiter Veriﬁcation feature. When the key is in the On position (not cranking or running), an rpm signal is sent to the tachometer to verify the unit's rev limit setting. With this function users can be sure of their rev limit settings before each drive To enable this feature, follow the procedure below.

Note: It is important to note that this feature should not be used with EFI systems. When activated,

an rpm signal is sent to the tachometer. With an aftermarket EFI system, this could activate the injectors causing a ﬂooding situation.

ENABLE REV LIMIT VERIFICATION

1. With the ignition switch in the off position, ground the Gray tach output wire.

2. With the Gray wire connected to ground, turn the ignition on without starting the engine.

3. Hold the Gray tach output wire to ground for seven seconds. (AT LEAST ﬁve seconds.)

4. Release the wire from ground before ten seconds have passed.

5. To conﬁrm the process has worked, cycle turn the key On. The tachometer should sweep to the

rpm limit set on the ignition.

To deactivate the veriﬁcation feature, repeat the process.

Playback Tach: If you use a playback tach, be sure to check the high rpm value prior to turning the key to the On position. When the key is in the On position, the rev limit will be displayed and may override the tach memory.

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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 (915) 855-7123. MSD technicians are available from 7:00 a.m. to 5:00 p.m. Monday - Friday (mountain time).

Limited Warranty

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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FRM30524 Revised 04/12 Printed in U.S.A.

MSD 83647 Installation

Specifications and Main Features

Frequently Asked Questions

User Manual