Regarding the resistor wire and whether removing it from the Pertronix or Dura Spark electronic ignition circuit would improve on performance? Installed the Dura Spark ll in both 65's some 15 yrs. ago and been working great with the resistor wire (pink) in the circuit. Recently got into a discussion with a member, which peaked my interest, so pulled up a couple Dura Spark diagrams and found the resistor wire can be installed or eliminated from the circuit. Not an authority on automotive electrical circuits, in particular ignition systems, am curious?

Suggestions appreciated!!

 

I would not eliminate the resistor from the Duraspark II unit. The system was designed with this resistor, and there have been many cases in the 80-86 truck forum above where people have ran without one for various reasons, and they run into trouble. It usually makes the ignition module fail after a period of time, but leaking/overheating coils can result also.

I am not sure about the Pertronix. If they say it can be run with or without, then I would believe what they say. If they say it needs it and you don't put one in, then look out for trouble.

To put it in simple terms, when the module, whether it's Pertronix, GM HEI or Duraspark II complete the circuit to the coil, initially the coil looks like a dead short to the module. The current is very high. As the coil "fills up" the current goes lower and lower. That's how it works, it stores the energy in the primary coil, and then when the circuit is opened by the module(or points in the old days) this stored energy is released into the secondary coil and stepped up to a very high voltage. The resistor has a really low value, usually somewhere around 1 ohm. When the current is initially high, the resistor limits this current to a reasonable level.

The GM HEI does not use a external resistor, it has circuitry inside the module that controls the current and keeps the module and the coil from overheating. The Ford TFI also controls the current and does not use a resistor.

 

Not familiar with the Pertronix either, have not come across a diagram of the pertronix circuit to compare? The current set up installed 15 years ago in the 65 has been working fine, just curious when the topic whether performance improved by eliminating the resistor wire?

Dave F., Greatly appreciate the information!

 

Eliminating the resistor will give a hotter spark. That's why the factory always wired a resistor bypass when starting, with the bypass either on the starter relay or made into the ignition switch. This gives a hotter spark during starting for quicker starts, especially in cold weather. The battery voltage is down anyway during cranking, power being robbed by the starter. But this is done momentarily during cranking only.

I am sure eliminating the resistor will give a hotter spark and improve performance, but there is no point when the module self-destructs from doing it permanently.