INSTALLATION INSTRUCTIONS

7

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 12). 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.

The MSD Ready-to-Run Distributor has an optional built in Rev Limiter Verification feature. When activated, it

will display the rev limit setting at key-on. This feature is not activated from the factory. 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.

VACUUM ADVANCE

Your distributor is equipped with an optional

vacuum advance canister. Vacuum advance is

generally used to improve cruising economy

and driveability, depending on the application.

The chart in Figure 13 shows the relationship

between engine vacuum and the amount of

ignition timing advance.

To connect the vacuum advance, connect a

vacuum hose from the canister to a ported

vacuum source on the carburetor or throttle

body. Ported vaccum sources are located

above the throttle plates so there will not be an

excessive amount of timing advance at idle and

lower engine speeds.

TO

TACH

OPTIONAL

PROGRAMMING

SWITCH

JUMPER

GRAY

Figure 12 Setting the Rev Limiter.

0

2

4

6

8

10

12

14

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910111213141516

Degrees of Advance

OE Non Adjustable Vac. Adv. 1808

Figure 13 Vacuum Advance and Timing Chart.