I then found this post regarding trying to run a 12 volt rated ignition coil after a ballast resistor instead of a 6 volt coil .
"""Now: You ask about a 12 volt coil working on 6 volts. I know this is math and most people don't like math but since you're developing a magnetic field within a coil using six volts, when that field breaks down (which is what breaker points do) you should get a spark. That coil is designed to work on 6 volts and its output should be around 12,000 volts. But if you use a 12 volt coil that may be designed to give you a 12,000 volt spark, powering it with only 6 volts will NOT give you half the power (AKA 6,000 volts) but you'll get 1/4th the spark power. In other words, 3,000 volts. WHY? Because of the inverse square law, which states that energy applied over an area will be four times weaker at half the voltage. """
"""Now: You ask about a 12 volt coil working on 6 volts. I know this is math and most people don't like math but since you're developing a magnetic field within a coil using six volts, when that field breaks down (which is what breaker points do) you should get a spark. That coil is designed to work on 6 volts and its output should be around 12,000 volts. But if you use a 12 volt coil that may be designed to give you a 12,000 volt spark, powering it with only 6 volts will NOT give you half the power (AKA 6,000 volts) but you'll get 1/4th the spark power. In other words, 3,000 volts. WHY? Because of the inverse square law, which states that energy applied over an area will be four times weaker at half the voltage. """
