Question about ballast resistors

[Milton]

Originally Posted by mngreen

I recently tried to test the coil impedance but my ohmmeter is not sensitive enough to tell. With the resistor installed, my car runs well, which it also did before installing it.

What happens if a generic ballast resistor is installed in a 12V ignition circuit with a coil that already has an internal ballast? What would be the effect(s) on the running of the engine? Would it even run? What about the condenser?

Since we are trying to solve the same problem, here is the solution that I used today. I hooked up the mystery coil to the 12v battery with the cars amp guage in the circuit and read +-2.5 amps. I did the same with a Mallory Promaster coil in series with a ballast resistor and read +- 2.5 amps. I moved the wire to omit the ballast and presto, I got a reading of +-5 amps. Obviously the mystery coil must have an internal ballast or, at least be able to handle the 12v without frying the ignition module.

That fact that the coil voltage is cut in half with a ballast would mean that an internal ballast with an external ballast would drop the voltage to about a third across the coil. This was low enough to expose the weakest plug of four and allow it to foul. I have removed the extra ballast and the plug cleared and I am confident that the ignition module will survive. (I hope)

Another plus, who wants to hang an ugly ballast on their firewall?

[Purdy Swoft]

Originally Posted by James Rogers

Next time you foul a plug just pull the connector to that plug away from the dist cap just enough to make the spark to jump a gap. It will clear a plug in seconds. This is because when a spark jumps a gap it intensifies and burns hotter. Try it next time, works great. and easier.

Just to add to what James has said. Here is what I do that works on the same principal and gives a little hotter spark to all of the spark plugs, all of the time . The Popular, mechanics handbook that many people have recommends a gap of .025 between the rotor tip and the plug wire contacts inside the distributor cap body. This is a conservative setting and will work ok. If you want hotter spark at the plugs open the air gap at the rotor tip up to .035. I have been running this gap for many years on all of my model A's and it makes a difference. A gap wider than .035 will give even hotter spark but will strain the coil. This is a small mod that doesn't show. I figure that every little thing will add up when souping up the original distributor.