Ive got a 68 SS chevelle thats got a bulit motor easily pushing 475 horses but the only problem is: starting it is a 50 50 deal sometimes it does sometimes it doesnt. The car has Petronix Electronic Ignition in it I dont know if that would have something to do with it. It will usually start when its stone cold but when its been driven just little it will die. I thought maybe it was the starter/ soleniod being overheated by the headers so we switched to a gear reduction starter and got it away from the headers and it did it again after being driven to a gas station. Im at my wits end does anyone have any ideas of what it could be and how to fix it? I think its the ignition switch. HELP! thanks.

If it dies after driving it for awhile than this eliminates the starter. The starter is out of the ignition circuit once the car is running. The ignition switch could be the culprit if something (a mild short somewhere) is causing one of the ignition circuits from the switch to get hot. I'm not sure exactly what type of engine setup you have here but it sounds like vapor lock.

Did you replace the STOCK switched 12 Volt wire to the ignition? It is a resistor wire and will drop the voltage to the module to protect the points (which are no longer there). The module needs a full 12 Volts. This is a common problem with after market ignitions. It doesn't usually kill the motor, but it's worth checking. I have seen old/worn resistor wires get very lossy with temperature.

Chuck