After a successful engine break-in. I had to rig the HEI to get a constant 12 volt source.

I ran a new 12ga. wire directly from the HEI to the fuse panel. When trying to start for the break in, every time I went from ignition "on" to "start" my voltage would drop from 12 to 4 volt. I then tried to hook up the other terminal on the starter (yellow wire) and splice it into the new 12ga. HEI wire thinking that it would boost the voltage to a constant 12 volt, but it did not work. (still dropped when I cranked) I am now stuck on how to find a constant 12 volt source that turns on and off with the key. Any suggestions?

Much obliged

Boucher