I'm cleaning up the engine compartment on the '72 and the guy who had it before me just ran from the fuse box a separate 12v wire to the HEI. Fenders are off and I've got easy access the the bulkhead connector. There's an ign/start wire that is hot at the right times. I believe it is the one that went to the coil + before (red and about 14 ga). I test lighted the red wire at the bulkhead connector at 12.2 v and around 12 at where it had been cut. The red wire says resistance on it. It does not at all look like one of those fabric covered beauties of yesteryear. (I understand those had more like 9v at the coil) .2 v is not much of a voltage drop. Is there any reason I cannot use that wire for my HEI +? Is the wire too small for the amperage the HEI will draw? I'm afraid the right answer is to pull it and replace it with a 12ga. I know I've read that - I was just surprised it had so much voltage as is. I don't really want to unwrap the harness if I don't have to. Help! I'm tired and trying to justify a lazy shortcut. LOL As I type my answer is clear. Ok. I'll replace it... still curious for everyone's comments.

If it is resistor wire, the voltage will drop under LOAD. If you measure it "open" with no load on it, it will measure full voltage.

Unwrapped, replaced with 12ga wire, ready to go. Not that big a deal. It's those finish details that get tempting to skip.

Interesting tidbit though. After getting the usual and expected, "dude, what we have is on the wall" at O'Rielly, I headed home and figured I'm driving right by Autozone, might as well stop. The Autozone actually had a "GM connector assortment" that had 2 of those wierd blade connectors and a bunch of odd others ($10). I can't believe they had such a thing. I spent about an hour unsuccessfully trying to open the old one to salvage it for reuse assuming I wasn't going to be able to find a replacement.

If the original resistance wire is not attached to the coil it will always measure 12 volts. Also the points need to be closed to see the voltage drop.