Duraspark Conversion
Convert those points to a trouble free ignition!

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Duraspark II electronic ignition was used on 1977 to 1984 Ford V-8 passenger car and light truck engines. This article refers to the Duraspark II control module with a BLUE strain relief bushing, one 4-pin connector, and one 2-pin connector. Another version of the system has an additional 3-pin wiring connector, and two YELLOW strain relief bushings. I never used that module so can't give any help.

Duraspark II uses a variable reluctance magnetic pickup in place of traditional breaker points. The signal from this pickup is amplified by the control module to drive the ignition coil. The module holds a fixed dwell time, and features automatic retard while cranking to reduce the load on the starter motor.

The high voltage ignition coil, wider spaced terminals of the distributor cap, and 8mm silicone insulated high tension wires permit the use of wider spark plug gaps. This results in a more powerful spark which is more likely to ignite the air-fuel mixture. Due to the higher voltage operation of the system, silicone dielectric compound should be applied to the insides of the spark plug wire boots, at both the cap and plug ends. This special grease is available at most auto parts stores, or under Ford part # D7AZ-19A331-A.

The larger diamter cap and better wires are not required, however, if the older tighter spark plug gaps are maintained. Under some circumstances you may need to retain the old style smaller cap. For example, you might not be able to fit the larger cap under a Monte Carlo bar in an early Mustang.

This ignition system offers the benefits of reduced maintenance, smoother engine operation with improved idle, better fuel economy, and reduced emissions.

Duraspark II Major Components

Duraspark II module

The Duraspark II control module has a BLUE strain relief bushing, one 4-pin connector, and one 2-pin connector.

Duraspark II distributor

The Duraspark II distributor uses a magnetic pickup in place of traditional breaker points. Most articles that I have seen on the internet talk about changing out the entire distributor, This is NOT required. You can take the breaker plate, pickup, upper shaft, and reluctor out of a dura-spark distributor and put it in your housing. All V8 breaker plates are the same!

Duraspark II distributor cap

The Duraspark II distributor cap is larger in diameter to allow the high tension terminals to be spaced farther apart. This prevents crossfiring with the higher coil voltage. The cap is made in two parts; the lower section is an adapter to fit the standard Ford V-8 distributor body. The rotor is longer and taller fit this cap. Yes, it even fits an old points distributor!

OK, here it is, Step By Step. It's easier to do with the distributor out, but I have done this with it in the car.
1.  Remove the cap and rotor 
2.  Remove the points and condenser 
3.  Remove the two screws and one E-clip that hold the vacuum  advance can on the distributor. 
4.  Lift the arm of the vacuum advance off the pin that it rides on and pull the assembly out. 
5.  Align the movable part of the breaker plate so that the hole in the center will clear the distributor cam. 
6.  Remove the two screws that hold the breaker plate and the primary wire in the distributor and remove the wire and plate. 
7.  Reach inside the top of the upper shaft and remove the peice of felt (the one that is supposed to get a drop of oil each time you change points). 
8.  There is a strange little wire clip holding the upper shaft down. Remove this by prying the two wire ends apart (2 pair of hemostats work great for this). 
9.  Now, take the advance springs off their pins, and the upper shaft will come off. 
10.  Re-assembly is the exact reverse, except the reluctor is a seperate piece that slides on and is held in place by a roll pin (see diagram). Get the breaker plate and all advance parts installed and working before you put the reluctor on, as they tend to crack when you pry them off. 

Wiring the Duraspark II

This ignition system is a popular swap into earlier cars and trucks. Wiring it up is quite straightforward. This is most easily accomplished by making a trip to your favorite junkyard and rounding up all the parts. Be sure to get the wiring harnesses connecting the module, distributor, and coil, as well as the male end of the 2-pin connector and some length of its wires. Note that the colors of the wires shown in the diagram below are at the module itself. The wires in the harness tend to be different colors on different cars and years.

Power is supplied to the BATT or + coil terminal in the same fashion as the older breaker point ignition. Under normal "run" conditions, power comes from the key switch through a length of resistance wire (0.8 to 1.6 ohms). This wire is normally pink and is found under the dash. During cranking, this resistance is bypassed by a wire from the "I" terminal on the starter relay. In most applications, the wire that used to power the coil can power the new coil.

The system is grounded through the black wire in the harness to a point inside the distributor.

Only one new connection is required. The module receives its power through the red wire in the 2-pin connector. This must come from the key switch terminal that is "hot in start or run". If your car has an idle positioner solenoid, the wire powering that may be used to power the module.

Optionally, but a good idea, the white wire in the 2-pin connector is connected to the "S" terminal on the starter relay. This is used as a cranking indicator to the module, to retard the timing slightly to ease the load on the starter motor.

Use the factory harness for the rest of the wires. The green wire runs from the module to the TACH or minus coil terminal. This is where you can connect a normal tachometer. The orange and purple wires from the module run to the pickup inside the distributor.

Duraspark II wiring diagram

Additional Notes on Conversions

Retrofitting the Duraspark II system to earlier small block V-8 cars is a popular swap. A few things should be considered when selecting the parts.

Distributors do not physically interchange between a 302 and 351W. 351W engines have a larger oil pump driveshaft. The end of the distributor shaft is also larger to accomodate this difference. The 289/302 distributor shaft diameter is 0.467", 351W is 0.531". At the junkyard, small blocks tend to all look alike. Be sure to go to the junkyard armed with a 1/2" distributor wrench. On cars loaded with power steering and air conditioning it can be quite a challenge to remove the distributor hold-down bolt without the proper tools.

Also be sure to use the correct distributor drive gear. The material must be compatible with the camshaft. Most normal cast iron camshafts require a cast iron distributor gear. Hydraulic roller camshafts are generally steel, and require a steel gear. Some aftermarket camshaft manufacturers specify the use of a bronze gear. Gears in all combinations of size and material are available from Ford Motorsport.

An old points distributor will have a hole that the primary lead went thru vice the U-shaped notch needed for the Dura-Spark wiring. Just use a razor saw or a fine tooth hacksaw blade to cut down the sides of the hole to turn it into the U-shaped notch. De-burr it with a jewler's file or some emery cloth.

With just a little effort, the cover on the Dura-Spark OEM module polishes up and looks great. The replacement part lacks the snazzy fins... 

 I have used several coils with this setup. The original Dura-Spark Coil, An Accel Big Yelloy 45Kv coil and a Jacobs Magnetic core coil. Believe it or not, the Dura-Spark coil gave me the best start and idle when I was running a bigger cam.

 If you wind up doing this for friends, you may find yourself with a box of upper shafts. Take a good look at them. There are several different lengths on the mechanical advance limit slots. A little tuning tip... 

Speaking of centrifigal advance, you may note that this swap is the perfect opportunity to put some lighter springs in that distributor. Go for it. If you are running an automatic, put both light springs in from a re-curve kit. You actually can feel the difference, unless you can't get good enough gas..

Speaking of vacuum advance, one of the articles mentions adjusting the Ford vacuum advance can. Not all of them have this feature, and I recommend you get an aftermarket unit if you want to tweak. I have had the adjustable orifice screw sucked out of an OEM can after tweaking it a few times trying to get rid of a too-much vac advance surge.

The control module doesn't like to get overheated. Be sure to mount it somewhere away from heat sources. (if such a place exists under a hood)  I have seen the potting epoxy running down an inner fender when this tip wasn't observed!