My car is a '67 chevelle equipped with non-stock 350, MSD 6A ignition box, new and fully-charged battery. Okay, here's my problem. I turn my key and nothing happens. No click, no engine turnover, nothing. This happens about half of the time I try to start the car and it doesn't seem to matter if the engine is hot or cold (although it happens more frequently when the engine has been running a while). The only way I can get the car started when this happens is to turn the key to the ON position and jump the solenoid against the positive with a screwdriver. So far, I have cleaned all wiring harness connections that I could find on the firewall. That didn't fix the problem. Help!!!