Be sure that the box/motor/chassis grounds are all perfect, and find out what the ohms resistance is supposed to be for the coil and ballast, and make sure they are all least as much resistance as the original design of the system. Any less resistance puts a heavy load on the box and can fry it. That is the info I got, but I chickened out and bought an MSD Streetfire for my street Dart for peace of mind But the thing runs now with a good, fat spark!