The breaker points, coil and distributor type ignition system that came stock in our Econolines was invented by Charles Kettering about 1913. The amazing thing is that it is basically unchanged from the original design. Originally cars were powered by 6 volt batteries. This is important to know because the ignition system was also designed around 6 volts. When the battery voltage was increased to 12 volts, (primarily to make another one of Ketterings invention, the electric starter, work more reliably in cold weather) the higher voltage caused problems with the breaker points.
Voltage is what enables a spark to jump a gap, the higher the voltage the more "pressure" there is to jump the gap. In this case he gap is the opening between the breaker points. The reason this is critical is that that spark may not look like much, but it actually heats up to about the same temperature as the surface of the sun! This in turn burns the contact points leaving them pitted increasing the resistance to current flow when the points are closed. The simple solution: add a resistor inline with the ignition to dropp the voltage back to about 6 volts.
If you are used to working on Fords, you may not even be aware of this added resistor. Other manufacturers often added a ceramic resistor under the hood, but Ford used a special piece of high wire built into the wiring harness. This wire is sometimes covered with cloth insulation to protect the other wires from the heat generated by the high resistance of the wire.
Understanding that the stock ignition is designed to operate at about 6 volts is important when you start thinking about upgrading the ignition to more modern technology.
Last edited by AZ SuperVan on Sat Nov 29, 2014 8:55 pm; edited 1 time in total