MSD CONVERSION
The stock Duraspark II ignition on the carbed 5.0's is actually a descent high voltage ignition. The stock Duraspark ignition is already capable of supplying higher voltage than most stock ignitions. It's simple design and easy of installation makes it a popular swap into all types of hot rods. Ford also makes a High Performance Duraspark II ignition control box which is basically a Duraspark II unit with better high rpm performance and a built in soft-touch rev limiter. But for about the same price you can purchase an MSD ignition system that will out perform the Duraspark hands down. There are other companies that also make high performance ignition systems to replace Duraspark II ignitions with similar results. Below is a suggested approach to designing and installing an MSD ignition.
Ignition Control Unit! MSD makes many different ignition control units. For the street Stang I recommended the MSD-6AL (MSD-6420) ignition control unit. This is a very respected ignition system and has been around for years. The MSD-6AL unit comes with a built in soft-touch rev limiter to protect your motor from over revving. The MSD 6AL ignition system comes with complete instructions for wiring the MSD into any type of ignition or by itself. MSD also makes an assortment of adapters for their ignitions to directly hook into existing stock wiring harnesses so no cutting is required. Note: Depending on the way you wire the MSD and if you are using the stock Tach in the dash you may need to order this Tach adapter. (MSD-8920)
Coil! Really any good performance coil will do. I like sticking with parts that were made to work together. The MSD-Blaster coil (MSD-8200, 8202, and 8203) are very nice coils, which puts out about 45,000 volts of juice and works great with the MSD-6AL ignition unit.
Distributor! The stock distributor can still be used as long as the advance curve is changed. If you run the stock distributor on a modified motor you will get poor results. Crane makes a kit to change the advance curve and I would suggest doing this if you plan on using the stock distributor. MSD makes a very nice billet distributor. (MSD-8582/302 and MSD-8584/351W) with a mechanical advance. The curve is adjustable with easy to change springs and stop bushings. The distributor comes with detailed instructions of the advance curve and graphs to help you choose the best curve for your application. The distributor is also capable of being locked out so that a timing computer can be used.
Multi-Step Retard Unit! The retard unit is used to retard the timing to keep a nitrous powered motor from over advancing as the nitrous is applied. If you plan on running nitrous this unit will need to be installed. MSD make several multi-step retard units that will work in just about any application. (MSD-8739 2-Step, MSD-8737 3-Step, MSD-8972 Multi-Step) Consult MSD for your application.
Boost Timing Master Unit! MSD makes a nice boost controller for superchargers. (MSD-8762) It is used to retard the advance as the boost increases. If you will be running a supercharger this unit will need to be installed.
Timing Control Unit! MSD makes a two timing computers. One is a Fixed Curve Timing Computer (MSD-8980) and the other is a Programmable Timing Computer. (MSD-8981) Each controls the amount of timing at startup and as the engine speed increases. One is fix and the other is programmable. Refer to MSD for a description of each computer.
Spark Plug Wires! Don't use anything less than 8mm. Apply a liberal amount of silicone dielectric compound to all the plug boots (at cap and plugs) and also a small amount to the rotor button.
The following are some helpful tips for installing the MSD in a 85 carbed Stang
MSD supplies instructions for ways to hook the MSD to your Stang. Either way will work. I recommend removing the Duraspark all together and using the MSD by it self. If you do this you will have to buy an adapter from MSD to make your stock Tach work. (MSD-8920) The stock Tach will not work with the standard MSD Tach lead due to the fact the negative trigger wire from the DuraSpark ignition is used to run the factory tach. I installed the unit where the windshield washer and radiator overflow box used to be on the drivers side inner fender well. The MSD can be mounted anywhere so the spot is really up to you. I have seen people go as far as installing it in the inner fender well above the plastic wheel splash guard.
The Blaster coil can be mounted anywhere as long as it is within coil wire distance from the distributor. The factory mount is on the top passenger side of the manifold. I relocated mine and installed it on the drivers fender next to the MSD 6AL box to reduce the amount of engine heat and vibration it would be exposed to.
The MSD distributor comes with a cast gear on it. The 85 Mustang has a roller cam in it and requires a steel gear. The MSD distributor comes with the 2 heaviest silver springs installed and a stop bushing that cuts off the advance at 20*. This is a good setting for the stock motor with no big mods. If you have a modified motor try the two blue springs to start and work from there following MSD's instructions. Remember if you set the base timing at 10 degrees then at full advance it will be 30 degrees. This can be adjusted up or down by switching the stop bushings or timing.