Wire HEI to 68 Cat
 

My 68 has an HEI wired into it already but I don't like the setup. The PO ran a wire from the HEI thru the firewall and into the block using an ACC terminal. So that he didn't fry the HEI he placed a fuse and switch between them. The switch is a PITA and I would like it to just fire using the key. I was poking around under the dash and noticed that the yellow wire coming from the key switch was hot during ign 1 and ign2 (cranking). Should it be safe to just wire my 12v HEI to the yellow wire coming from my ignition switch? I'm sure someone has performed this already. Thanks in advance.

Mike

According to the 65 FSM, the yellow wire is the ign2 wire, and should only be hot in start. I would imagine that 68 would be the same? Being that the PO wired the HEI to a switch, you may want to poke your head under the dash and try to see what other wiring modifications have been done.

If the yellow wire is hot in ign1 and ign2, then you must be getting your readings (probing with a light, or a voltmeter?) after the ign1 wire and ign2 wire join (after the resistor). You should get 12v in ign2 and only 6v in ign1. If that's the case you can't use that for the HEI. Maybe the PO removed the resistor from the wire. If you get 12v in ign1 and ign2, you should be able to use it.

http://www.supermotors.net/getfile/1...ion-switch.jpg

There are a few different ways you can wire the HEI. The factory transistorized ignition needed constant 12v like the HEI does. The factory accomplished this by shorting ign1 to ign2 at the switch. There was a "shorting bar" that went from the ign1 terminal to the ign2 terminal. This takes 12v from ign1 terminal and runs it down the ign2 wire, bypassing the resistor. That's how I did it when I installed HEI in my dad's 67. (I replaced the small factory wiring with some 10 gauge stuff). If you don't want to replace the wiring, but don't mind making your own shorting bar, you can use the factory wiring to activate a relay, and have the relay power the HEI.

You can also find and remove the resistor, and use the original wiring.

Should be a pink wire off the iginition key switch iunder dash but you likely will need to "Y" into the circuit for the HEI plug from the "R" terminal on the starter solenoid to provide the need 12 Volt boost while cranking otherwise it may not fire while cranking due to a voltage drop.

I know as of right now my yellow wire lights up during ign1 and 2 but I have no idea what the voltage is. I'm waiting for the meter I ordered from Ebay to show up, then I will know more. Thanks for the help so far.

This is exactly how I wired the HEI in my 67 wagon.

Importsmasher

So 1 wire from the pink and 1 from R?

Exactly, the pink under the dash near the key switch then at the firewall underhood bring up wire from R on solenoid from starter (this is a good reason why I use a Ford solenoid on fender) , put both wire together in one side of a connector then on other side of connector continue one wire with Female HEI connection to plug in and go !

The factory points coil wire + wire if intact usually has factory resistor wire from starter crimped together right were it bolts on stock coil and its supposed to be reduced under 12 volts as far as factory harness goes and clipping the pink wire under dash wiuth disable it and would removing original resisitor wire. Strangely my 68 GTO I had till recently had already been swapped to HEI and they had used that points coil connection and it worked but all the mid to late 60's Pontiacs I have converted to HEI particularly 65,66, and 68 I did what I described initially. Works like a champ. Skipping the R terminal will provide much grief when you go to crank on it if only using power form the pink wire. I think later Pontiacs changed something in the harness design as I recall my 70 TA I put HEI on in worked solely off the fuse box unlike every 68 and older I tried that on.

Thanks a ton! Hopefully I can get her squared away this weekend for Mondays cruise nite. I'll update when I do. Thanks