HEI conversion help

BillGrissom said
75slant6,
We assume you have a 1975 slant. I don't know that wiring schematic. In my cars, the thicker brown wire is only hot in "crank", termed "IGN2" to bypass the ballast. But it is not hot in "run", where "IGN" (blue?) gets powered. Since IGN isn't hot in crank, you need to connect both and run to both your ECU and coil+, so the ignition is powered in both crank and run. Coil- doesn't connect to ground. If you tried that, I bet your coil got real hot. Coil- is how the ECU controls spark (termed "low-side switching").

You have to figure out the coil wiring because you are using a purty after-market E-core coil (Ford TFI connector?). Had you used the GM 8-pin module and GM "external coil" (1985-95 V-8 pickups), no figuring since a short GM cable connects the two for easy plug n' play. That is what TrailBeast kits for those who can't go to a junkyard. I just picked all the parts a few weeks ago for a friend w/ an earlier Corvette, plus the knock sensor/module, and nice plug wires, all for ~$40 on half-off day. In his case, I grabbed the whole distributor, but we just need the 8-pin module inside it, and take the pickup connector.

That's about it Bill.
On my systems the module gets it's power from one of the coil terminals to power the ECU. and not knowing how it's wired up makes it kind of hard to answer the questions.
Bill hit it on the nose though, when he said tie the start and run wires together and then straight to the coil +
The other red wire off your coil positive is maybe powering the ECU?

The picture shows how you tie the two wires (start and run) together and use that for the coil ignition positive.
This gives the coil 12v in both positions.

As bill said, the coil ground goes to one of the module terminals and not just grounded.