Both the feed wire to the ignition switch, and the HEI hot lead on GM original equipment wiring is 10 gauge. The ignition switch is fed directly from the battery cable terminal at the starter through a fusible link, not a fuse, with a 50 amp rating, IIRC. It must carry the surge current of the starter solenoid pull-in winding (up to 30 amps) plus the load of the ignition system.
"All ignition systens work on 6 volts"- - - - -WRONG! Point-type ignition coils designed for 12 volt ignition systems require a ballast resistor to drop running voltage to approximately 9 volts. Why? Because there's a bypass circuit that delivers straight battery voltage to the coil during cranking, usually about 10 volts, and for the coil to work efficently on a cold start, it must be able to work at full output at 9 or 10 volts. After the engine starts and the charging system kicks in, voltage can be 13 to 15 volts, and a resistor is needed to prevent the coil from overpowering the points and burning them due to high primary current.
Solid-state ignition systems don't use points, so they can use full battery voltage and high current draw coils. That makes over 50,000 volts available to fire the spark plugs, instead of 20,000 volts or less from a point-type system.
If you're going to protect the circuit from the battery to the ignition switch, use a 40 or 50 amp circuit breaker, or a #10 fuse link, not a conventional fuse.
Jerry
Last edited by Hotrod Lincoln; 05/01/2008 1:00 AM.
