Re: HOW??? Do I convert to battery ignition on a 73 Chrysler 70hp?
Putting a ballast resistor/coil ignition system is not necessarily a bad idea. It will provide a hotter spark during cranking. Basically, ballast resistor type ignition systems place a set of relay contacts across the ballast resistor that is in a series electrical path with the primary side of the coil. During cranking the contacts are closed which bypasses the current around the resistor, effectively removing it from the primary circuit. Once the motor is started and is no longer cranking, the relay contacts open and reintroduce the resistor into the primary coil circuit. This scheme provides high primary current during cranking and lower primary current while running. In short, the coil more or less gets a current boost during starting, resulting in a nice hot spark to get the motor started.
The downside of ballast resistor ignitions is the parts count and wiring complexity. In a non-ballast type systems you simply have a set of points, condensors and primary coil in the primary circuit. In ballast type systems, you have points, condensors, the coil, the resistor and a relay + all the additional wiring. Either scheme will potentially work. However, if you are experiencing a weak spark during cranking the ballast type system will prevail.
Personally, I would go with the simpler non-ballast approach first. If I determined the cranking spark was weak, I'd change to the ballast type system.
To identify a coil (wheather ballast resistor type or not), I'd look up in a parts application guide some old vehicles (60s/70s) and see if a ballast resistor is required. If a resistor is shown you then know the status of that system and can use the coil from that system if desired.
