This Mustang Parts Installation Guide Works For
Installation Time: (approx) 2 Hours
Note: The terminals of the Ready-to-Run Ford Distributors require spark plug style terminals. You may need to change the terminals and boots of your wires. MSD offers two kits, PN 8849 or PN 8848 that are supplied with nine boots and terminals.
Before continuing with the installation, here are a few definitions you should be aware of:
Initial Timing: This is the base timing (also referred to as idle timing) of the engine before the centrifugal advance begins.
Centrifugal Advance: The centrifugal (or mechanical) advance mechanism is made up of weights, springs, advance cams, and an advance stop bushing. The amount and rate of advance that your distributor is capable of is determined by the centrifugal timing. If you ever wish to lock out the centrifugal advance, refer to the centrifugal advance section.
Total Timing: This is the total of the initial timing plus the centrifugal advance added together. Example: 10° Initial + 25° centrifugal = 35° Total Timing. (When checking Total timing, disconnect and cap the vacuum canister and plug the vacuum line.)
Vacuum Advance: The vacuum advance will advance the timing up to 10° during partial throttle driving (with 15 lbs of vacuum). The vacuum line should be routed to a ported vacuum outlet above the throttle plates.
Note: MSD Distributors are supplied with the heavy (slow) advance springs and the 21° stop bushing installed. This is to prevent detonation in certain applications. Review the information on pages 2-3 to determine the best advance curve for your application.
Tach Signal: The Ready-to-Run Distributor features a Gray Tach Output wire which provides a clean signal for most tachometers and even some aftermarket fuel injection systems. The signal output is a 12 volt square wave, 20° duty cycle. This wire is also responsible for programming the built-in rev limiter.
Rev Limiter: The Ready-to-Run Distributor has a built-in rev limit that can easily be adjusted from 2,000 rpm to over 10,000 rpm. The default is 10,000 rpm. To set the rev limiter, run the engine to half the desired rpm then ground the Gray Tach wire (a jumper is supplied) for approximately one second. Every time the key is turned to the On position, the tach will display the programmed rpm limit. See page 8 for the programming procedure.
The function of the advance curve is to match the ignition timing to the burning rate of the fuel and speed (rpm) of the engine. Any factor that changes the burning rate of the fuel or the engine speed can cause a need for an ignition timing change. Figure 1 shows some of the factors that will affect engine timing.
The timing mechanism of the distributor must make timing changes based on these factors.
Example: An engine has 11:1 compression, a high energy ignition and turns 5,500 rpm. With the specifications given, you will have to retard the timing for the high compression, low rpm and high energy ignition. By comparing the engine’s specifications against the chart, a usable timing guideline can be found. Engines with a combination of items from both columns will require a timing that is set in the mid range. Obviously a full technical explanation of correct ignition timing would be very complicated. The best way to arrive at a suitable ignition curve for your engine is to use the Ignition Timing Factors Chart as a guide and compare it to the Advance Graphs in Figure 4 until a suitable curve is found. When selecting your advance curve, use detonation (engine ping) as an indicator of too much advance, and a decrease in power as an indicator of too little advance.
The rate, or how quick the advance comes in is determined by the type of springs which are installed on the distributor. The MSD distributors are equipped with two Heavy Silver springs installed. These will give you the slowest advance curve possible (Figure 2). The parts kit contains two additional sets of springs which can be used to match the advance curve to your particular application. Refer to the Spring Combination Chart (Figure 3) for combinations that can be achieved.
To change the springs, remove the cap and rotor and use needlenose pliers to remove the springs. Be sure the new springs seat in the groove on the pin.
Three different advance stop bushings are supplied in the distributor kit. The distributor comes with a Blue (21°) bushing already installed. If a different amount of centrifugal advance is desired, follow the next procedure to change the bushings. The chart in Figure 5 gives the size and approximate degrees for the corresponding bushings.
If you do not want to use the vacuum advance canister of the MSD Distributor, MSD has supplied the distributor with a lockout mechanism. The Lockout bolts in the position of the vacuum canister and will hold the pickup assembly firmly in place. The installation is easiest with the distributor out of the engine.
Note: If no shims were required, use one beneath the washer of the Lock-Out Hold Down Screw.
Note: Do not forget to plug the original vacuum advance hose.
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.
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 14). The default rpm limit is 10,000 rpm and the limit is adjustable from 2,000 - over 10,000 rpm..
Note: This rpm confirmation only displays when the Gray wire is being used to trigger the tachometer.