[robert91gt]

Does anyone have a 68 wiring diagram or know why there is 2 wires for the positive side of the coil? I have a black/white and pink connected together at the coil. Both wires run into the harness at the firewall connector.
Thanks

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[gto4evr]

pretty sure one's a 12v line active in the start position only, and the other is a resistance wire running like 7v in the run position so your points don't burn up.

So....turning the key to start the car, it runs it up to 12v, then when the key's backed off to run, it runs at lower voltage through the resistance wire so the points don't cook.

[Jonsie]

Yep

[robert91gt]

Can I just cut the black wire at the firewall connector? I'm converting to HEI

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[gto4evr]

Originally Posted by robert91gt

Can I just cut the black wire at the firewall connector? I'm converting to HEI

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no, because you'll have no voltage in run. you need to run a 12v wire in the run position or the motor will start and then die once you release the key. you need a 12v feed to the HEI in the run position.

[robert91gt]

So just omit both wires?

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[gto4evr]

Originally Posted by robert91gt

So just omit both wires?

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depends on your source. you need 12v in both start and run positions to the hei. I'm not sure on the resistor wire if it still has power at the start position on the ignition switch. simple test with a test light after cutting it loose from the other wire at the eye on the coil. cut the resistor wire off, pop the coil distributor wire off the cap so it doesn't start, then have someone crank it while you test to see if that wire's getting any power during the crank cycle. if it is you could probably just cut both wires at the bulkhead and splice them both to a single wire to the coil on the hei. if it isn't I'd leave the 12v start wire in place and jump a feed off another wire that has power in the run position only. (you don't want the coil activated from the accessory position kind of thing)

a quick way through here is to run a wire off the fuse box from the IGN tap and splice it to the 12V start wire going to the coil right now. you can cut the resistor wire off and you're done. I'm just not sure the IGN has power during start phase, so that's why I'm suggesting leaving the current 12v wire in place. I guess you can do the same test on the IGN tap of the fuse box, if it's still hot during cranking, then that's the only wire you'd need.

[tjs72lemans]

As said, use the 12V ignition fuse box source. Tuck your old resistance wire aside rather than cut (in case you or someone wants to go back to points). Take the new lead to your HEI and call it done.

[gtokid1968]

Isnt it supposed to be a larger wire than the small one that ran the points? (IMMIC)

[DogMeister]

Mine's a '67, but the concept should be the same. There are IGN1 and IGN2 terminals on the ignition switch. One is hot during crank, the other is hot during run. The resistance wire is connected to the run terminal (I forget which is which). When I put my HEI in I eliminated the resistance wire and jumpered IGN1 and IGN2 together for 12V during start and run. Have been running that way for several years.

Obviously the difficulty in doing that in a '68 is the lack of accessablility to the ignition switch terminals.

[Geoff]

Easiest fix:.

The HEI draws more current than points ign & is very voltage dependant. Reducing voltage drop to the HEI will increase spark energy. You bought a HEI to improve spark performance, why not ensure you get max performance from it??
So use a simple 4 pin Bosch relay.
Ground one side of the relay coil. The other end of the relay coil, you connect ALL wires that were originally connected to the [+] terminal of the stock coil.
Relay contacts. Connect one to the HEI 'Bat' terminal.
Connect remaining contact to either the large terminal on the alt...or the battery [+] terminal, with a 15 amp inline fuse.

Done!