Ford Duraspark 2 Ignition System
The Ford Duraspark II electronic ignition system is a great upgrade and economical solution over a points type system. It is pretty much maintenance free. The Duraspark II system was used on all small blocks starting in 1977. The system is solid for most mild steet rod applications.
There are four basic components to this ignition system - the distributor, ignition module, the coil, and the wiring harness.
The Distributor - The key here is to get a distributor that is compatible with your cam type, has vacuum advance, and has a decent mechanical advance curve. If you are using a roller cam and you need a steel gear - use an '85 Mustang 5.0L GT distributor for a 5-speed. This distributor has vacuum advance and a great advance curve straight from the factory. If you are using a flat tappet cam your first choice should be an 82-84 5.0L Mustang HO distributor. This distributor also has vacuum advance and a good curve. Any 77-84 302 distributor will work with as long as the car was carbureted (NO CFI - throttle body injection), just don't forget to use a drive gear that is compatible with your cam.
Advance Curve Reprogramming - To get the most out of these distributors an advance curve should look like this: centrifugal advance - 0 @ 1,300 rpm, 11 @ 2,000 rpm, 20 @ 5,000 rpm; vacuum advance - 0 @ 4.5" Hg, 11.5 @ 8" Hg, 20 @ 12.5" Hg. Okay, so what's the big deal about vacuum advance? How about your gas mileage - with a vacuum advance distributor your gas mileage will be significantly higher than with a mechanical advance distributor alone. If it is a strip only car then it won't matter - vacuum or mechanical.
Ignition Module - This is really pretty simple - get the one with the blue color plastic where the wires go into the module. There are a variety of grommet colors but the blue one is the easiest to get. When mounting the unit be sure it is grounded good and away from high temperatures. Heat is what kills electronics so a little prevention up front will go a long way to long term life. The part numbers for this unit are as follows:
- GP Sorensen: EL107M
- Standard: LX203
- ECHLIN-Napa: ECHTP40
- Niehoff: FF402
The Coil - Just about any coil will work but stick to the good stuff - Stock, Accel, MSD, Mallory, or Jacobs. The stock Ford TFI coil is an excellent performer for the price. More on this in Part 2. Whatever you choose, mount it away from heat and vibration for the longest life.
Wiring Harness - It is always easiest to use the factory harness with the factory connections, but be careful, if you are fabricating your own harness do a good job of soldering or you will end up with electrical issues down the road.
Wiring diagram graphic - As you can see, wiring the Duraspark Ignition is pretty much straight forward. It is, for the most part, a "stand alone" system needing only one outside power connection. The control box gets its only power through the red wire in the 2 pin connector. This needs to be a ‘hot in start and run’ source. And a solid 12 volts. The white wire in the 2 pin connector may optionally be connected to the S terminal of the starter solenoid, this provides a cranking indicator to the control box, retarding the timing a few degrees for ease in starting. The rest of the wiring uses the factory harness. The color of the wires in the harness may differ for different years, but the colors on the control box and the distributor are the same. The green wire goes from the control box wires to the negative(-) terminal of the coil. This is where a TACH may be connected. The orange and purple wires run from the control box to the pickup inside the distributor. The black wire runs to the distributor housing and is the control box's only ground. It is a good idea to splice into this wire and run an additional solid chassis ground.
Odds and Ends
Use the cap and rotor combo appropriate for the year/application distributor you are using. And it is never a bad idea to get a premium cap with brass contacts. Under some circumstances, where you have space issues around the cap, you may need to retain the old style smaller cap but you can also step up to the larger diameter (EEC) version caps and rotors for better crossfire protection if you have the room. The cap posts are female instead of male, but once again follow the year application for the right cap /rotor and the matching spark plug wires. And speaking of plug wires stick to the name brand stuff for best results. Part numbers are in Part 2!
The Duraspark distributor is easily wired to an MSD or other aftermarket ignition system. The MSD can be used as a stand-alone or in conjunction with the stock module.
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