I have a 1985 F150 with a 351w. I dont know if im just over thinking this or not. Most likely im just over thinking this. I installing a ProComp H.E.I distributor for the easy and availability of parts. Currently the truck has TFI with all the emissions stuff either missing or not working. My issue that im having is that i dont know where to get my 12volts in start and in run. I was thinking of getting my 12volts by splicing in the ballast wire of the original ignition harness. Just either remove or splice before the ballast. I dont have wiring diagrams to help me out either. Im probally just over thinking this but any ideas will be grateful appreciated! Thank you!

 

You need more current than the stock coil wires can supply.
Use these wires to trigger a 30A fused relay, and use that relay to provide power to your HEI.

 

So hook a 30 amp fuse or circuit breaker to the battery + terminal, run a 10 gauge wire from this to the relay, and run another 10 gauge wire out of the relay to power the HEI. Hook the coil of the relay to the old Ford coil + wire to trigger the relay.

 

Thank you guys very much. The distributor I'm installing is all in one, the coil and module are with in the distributor. Coil is on top of the distributor. I don't have to wire it up separate. I didn't think I need that much current going to the distributor. That's why I was just going to go in front of the ballast resistor.

 

It will need A LOT of power, those systems are very hungry. The install instructions should cover that. Most I have seen are 20-30 amp circuits. It is best to not pull that off of the factory harness but by a relay as suggested. The factory wire isn't even a large enough wire to support it.

 

Then i will run a 10gauge wire from the battery to a 30amp fuse block to a relay. Then i will remove the ballast and use that wire to trigger the coil in the relay then run a 10gauge wire from relay to distributor just like the previous poster. Thank you guys for the input! Ill let you guys know if i havr any issues.