HEI upgrade wiring harness changes

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   One of the upgrades that I am making as I rebuild the engine in my 1980 Eagle is an upgrade to an HEI distributor. I am assuming (and research seems to confirm) , that they run on 12 volts all the time. I am also assuming, and need clarification, that the module that is on the fender that plugs into the main harness and the existing distributor is only for the stock distributor, and can be eliminated. The existing wiring on the car seems to have had some previous hack work and is somewhat suspect, so I was planning on unwrapping and fixing any problems, adding relays for the headlights and then re-wrapping  the harness as needed. All that to ask is it safe to eliminate the existing AMC/Motorcraft ignition module and its' associated wiring, and in doing so find and use a full 12 volt feed for my new distributor? I do have a 1980 TSM and also know how to read a wiring diagram, its just that the car was somewhat disassembled when I bought it so I am flying somewhat blind here and do not want to fry my new dizzy, or cause other problems down the road. 

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fhpdave Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: May/09/2014 Location: Galena Ohio Status: Offline Points: 445	Post Options Post Reply Quote fhpdave Report Post Thanks(0) Quote Reply Topic: HEI upgrade wiring harness changes Posted: Dec/01/2018 at 8:37am
	One of the upgrades that I am making as I rebuild the engine in my 1980 Eagle is an upgrade to an HEI distributor. I am assuming (and research seems to confirm) , that they run on 12 volts all the time. I am also assuming, and need clarification, that the module that is on the fender that plugs into the main harness and the existing distributor is only for the stock distributor, and can be eliminated. The existing wiring on the car seems to have had some previous hack work and is somewhat suspect, so I was planning on unwrapping and fixing any problems, adding relays for the headlights and then re-wrapping the harness as needed. All that to ask is it safe to eliminate the existing AMC/Motorcraft ignition module and its' associated wiring, and in doing so find and use a full 12 volt feed for my new distributor? I do have a 1980 TSM and also know how to read a wiring diagram, its just that the car was somewhat disassembled when I bought it so I am flying somewhat blind here and do not want to fry my new dizzy, or cause other problems down the road.
	Old enough to know better - young enough not to care

pacerman Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Joined: Jul/03/2007 Location: United States Status: Offline Points: 9060	Post Options Post Reply Quote pacerman Report Post Thanks(0) Quote Reply Posted: Dec/01/2018 at 1:55pm
	Yes the ignition module can be removed. Just make sure that you have a 12 volt feed to the new HEI. By the way the 1990 TSM supplement has a much better wiring diagram that the original TSM for 1980. The lettering is in block letters and is much easier to read than the "script" in the original volume. Joe
	Happiness is making something out of nothing.

Pdok Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Joined: Apr/03/2011 Location: Alabama Status: Offline Points: 1025	Post Options Post Reply Quote Pdok Report Post Thanks(0) Quote Reply Posted: Dec/01/2018 at 2:00pm
	I ran HEI for a while, just completely bypassed the stock ignition, but did not yank it out at that time (essentially same thing, but didn't cut wires). Absolutely run a beefy +12V feed to it. As I recall, there was a fusible link somewhere in the old ignition circuit... Your HEI is going to want the full feed, and no reason not to make it 10 or 12ga wire with a weatherproof soldered/shrink connect on both ends. No issues with HEI myself, makes it really simple. Remember to pay attention to the centrifugal advance springs and get an HEI with adjustable vacuum advance. I got one of the $70 eBay, and it worked great until I pulled it during the MPFI swapout. I've heard plenty about the dist gear chewing up cams, but mine wasn't in there long enough, if indeed it was chewing mine up. Dunno, but supposedly there are softer gears, or you can apparently reuse the AMC stock gear. I bookmarked this when I was looking at doing mine: http://www.4x4wire.com/jeep/tech/electrical/hei02/ Oh, and I absolutely recommend dual relays for the headlights! Sounds like you've already decided to do it, but that's a must for every old car I've owned and it helps tremendously.
	76 Grem X 258/904,4.0 head/MPFI, Comp X250H cam, Hughes springs, Clifford header, serpentine swap.

Pdok Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Joined: Apr/03/2011 Location: Alabama Status: Offline Points: 1025	Post Options Post Reply Quote Pdok Report Post Thanks(0) Quote Reply Posted: Dec/01/2018 at 2:01pm
	Forgot to mention, while you're into the electrical, you might want to upgrade the alternator and do a 3-wire conversion (as opposed to the 1-wire). Search the forum here and there's plenty on that.
	76 Grem X 258/904,4.0 head/MPFI, Comp X250H cam, Hughes springs, Clifford header, serpentine swap.