MG Car Repair: Ignition coils, ballast resistor, electronic ignition system

Question
I have a 1977 MGB with a Petronicx Ignitor electronic ignition system.I'm currently using the Lucas sport coil ( 3.0 ohms)coil.  I  purchased a Petronics flame thrower coil, and specs say 1.5 ohm. Directions say it can be used on a 4 cylinder for racing with no ballast resistor. But you should use one for normal driving. The system does not have the resistor now, but I have the original ballast resistor. Should I add it in with this coil?

Answer
Hi Bob,
I don't know what Petronics is talking about. The car used a 1.5 ohm coil because there is a resistor wire that feeds the ignition in the "Run" position and a straight bypass of the resistor wire to apply 12v to the 1.5 ohm (6v coil) coil in the "Start" position because the ignition system does not have a full 12v available when the starter motor is engaged. Most aftermarket ignition systems require a 1.5 ohm coil (6v coil) but I don't know what yours requires. There should be some instructions with the system you bought.
Howard