Expert: Brad Sears - 1/29/2011

Question
Hi there, I own a 1969 F-250 Good Humor ice cream truck. I've determined the engine is not the original 240 i6,it is in fact a 300 (due to the near 4" stroke) and one from 1974 or later due to the stock electronic ignition. I just finished detailing the engine compartment and as I ponder the newer ignition I wonder if I still need the ballast resistor. My solenoid sends 12 volts to the coil during cranking and the ballast drops it down to around 6 1/2 volts while idling.  I am running a 12 v coil however I am not sure the module and distributor are rated to continually run at the full 12 - 14.5 v? I've already gapped my plugs @ .40" and upon inspection found near average conditions, mild dark deposits. I'd like to bypass the ballast and improve my millage and performance. I guess my question, was this ignition originally desingned to run 12v coil without the ballast or is it required and if so, what rating, .7, 1.7 ohm?
thanks for any suggestions!

Answer
The ignition coil will not live without the ballast in the system. Increasing the voltage to the coil will not improve fuel mileage running at slow speed with a fair amount of idling. If you were turning the engine at high RPM all the time then you might improve fuel economy by removing the ballast but it would be marginal and would shorten the life of the coil. The coil is designed to run at 6 to 7 volts and when cranking the battery drops to around 9 volts so that when cranking to start the coil is receiving just a bit more voltage than when running.