Need Help With Wiring.

Electrical and Ignition

  1. Peter J Boncella

    Peter J Boncella Member

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    I have a 1971 Dodge Demon, it was originally a slant 6, I am putting a 360 from a 1974 Plymouth Duster in it. I have the wiring harnesses from both is there a way I can use one or the other or a combination of the two to make this work? also does anyone have a diagram of the wiring? thank you!
     
  2. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    There are differences in the two, I would stay with wiring "in the car" that is the car receiving the engine. Other than extending some wires, it should pretty much hook up

    If you are going to go with the factory electronic ignition, carefully unwrap the harness starting at the ECU connector and strip out the wiring. Two will go to the distributor connector, and other two will go to 4 pin ballast.
    The "power to" the ballast on the 74 is the two that are jumpered together at one end. That could easily be spliced to the same equivalent wire in the 71
     
  3. BillGrissom

    BillGrissom Well-Known Member

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    Using the 360 harness would be easier since the wires will reach each component. The slant-six harness likely has a multi-pin square connector on the passenger side which goes to the distributor and coil, at least one I got from a 1974 slant did. A 1974 would have the 4-pin ballast for coil and ECU, though you might need to drill mounting holes on the firewall for those. Personally, I wouldn't fuss with the old stuff. You can use your e-distributor to trigger a GM 8-pin HEI module which has a GM cable to their e-core coil. No need for the old ballast and a stronger spark. Many posts here. Easy pick from a 1985-95 GM V-8 truck or buy new parts kitted by Trailbeast here. You could even install a new HEI distributor for only $45 (ebay, Steve White Performance and others), courtesy of Ningbo of China. Wiring diagram links have been posted many times here (MyMopar, I recall).

    If your underhood wiring is as brittle as mine one, replacing all or most wires might be smarter, as I did. You can buy new 56 terminals for the bulkhead connector on ebay, and all the other connectors at websites (links posted before). The wires in your light harness and wiper harness might be OK, leaving just the engine connector to re-work. Also review the "MAD Bypass" for the alternator output, so the bulkhead connector doesn't melt.
     
  4. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    Disagree Bill, the 74 harness is quite different, plus it has the annoying 74 only seat belt interlock junk. It does not take much to untape and remove the wires for the ECU/ electronic ignition if needed
     
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    • Peter J Boncella

      Peter J Boncella Member

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      Ive got an MSD Distributor, will I need one their ignition controllers too?
       
    • Oldmanmopar

      Oldmanmopar Going left turning right FABO Gold Member

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      Just keep the 71 /6 harness in the car. You'll need to untape it and shorten the coil and oil pressure sending unit wires. The /6 uses all the same wires as the 360 except for the electronic ignition. That can be cut out of the 74 harness and installed using the schematic below. The harness from the 74 has a totally different firewall/bulkhead plug.

      Page10-1.jpg
       
    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      Which one? Part no?
       
    • Peter J Boncella

      Peter J Boncella Member

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    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      That's a magnetic trigger just like the old Mopar electronic. So if you use it with a Mopar module, yes, you'll need the Mopar electronic module wiring. The distributor connector does not look like it will connect, you'll have to splice something there

      Be aware of pickup "polarity". The trigger is essentially an AC signal, but depending on wire orientation, it will move the timing / trigger in time, google "rotor phasing"
       
    • Peter J Boncella

      Peter J Boncella Member

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      If I use one of MSDs digital 6AL ignition modules( https://www.summitracing.com/parts/msd-64253 ) will it hook up smoothly without any AC current causing potential issues with timing?
       
    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      Well look if you are going to go all MSD I would not even screw with the Mopar electronic harness at all
       
    • Peter J Boncella

      Peter J Boncella Member

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      I've not done wiring before, do you think its worth the near $300 for the MSD over trying to hook it up with the Mopar harness?
       
    • Mattax

      Mattax Just the facts, ma'am FABO Gold Member

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      No. You have enough to learn as it is and the digitals don't have a great rep.
      Choices:
      Use a points distributor set up for '67 273 w/ 4bbl Advantage - no wiring changes.
      Disadvantage if you drive a lot points need some maintanence and replacement when worn.
      Disadvantage is cost/availability if you want a dual point.

      Use the points distributor for a 273 HiPo with an MSD 6 or similar.
      Advantage - good advance curve for the engine, Little wear on the points.
      Disadvantage - cost of MSD
      Disadvantage - some wiring required but advantage is original harness stays intact.

      Use a Chrysler electronic distributor with an advance like the ones in the original Mopar performance ones,
      Plus MSD 6A.
      Advantage - no points to maintain. Original harness stays intact.
      Disadvantage - some wiring required.

      The last is the one I'd think about if you want electronic. Rick Eherenberg (sp?) sells a distributor supposed to be the same as the old Mopar Performance ones. FABO member Halifaxhops sometimes has them too (not new but just as good).
      If the car already had a Chrysler ECU on it, then I'd say just use that. But since it doesn't, the MSD 6 analogs is easier to wire up and still seems to be pretty reliable.
      HEI based setups are not as plug and play. Stick with something easy. All the ignition system needs to do is light off the fuel at the right time. When it is burning good more voltage or longer duration isn't doing anything. The most important thing is ignition timing.

      If the '74 360 still has its distributor, its going to have a 'smog' curve in it, even if it was a 4 bbl. You can use it if the initial advance is reduced by welding. I'm going to assume that's deeper than you want to get. But you can send it to Halifaxhops (he'll do the same thing without welding). Don't fall for the limiter plate chit chat. It can work but it can also not work depending on the situation. If it doesnt you'll be in for a ton of trial and error work.

      my .02 and then some.
       
    • Mattax

      Mattax Just the facts, ma'am FABO Gold Member

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      If your going to drive this car at night alot, then look at getting a relay harness. FABO member crackedback makes one for sale that is plug and play.
      The headlight wiring is the weakest part of the wiring on your car. The relays will not only help the lights, but reduce the maximum loads that have to pass through the bulkhead connector.
      Completely reversible and no cutting of the original wiring.
       
    • Peter J Boncella

      Peter J Boncella Member

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      Wiring Harness Photos - Google Drive Here are the harnesses I have, the Rear harness is still in the car. I am pretty sure the original one from the demon is a 4 point ignition, and the new for the duster is electronic. I try to follow diagrams and schematics from Haynes, and Chiltons and it seems like I just don't have enough wires.
       
    • Peter J Boncella

      Peter J Boncella Member

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      Also, can I just splice the connector from the old distributor on to the new? ive been told the other connector on the old distributor is something to do about Lean Burn.
       
    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      I have no idea what you have, There was no lean burn in 74, so unless you have some part of some harness or distributor out of an actual lean burn car I don't know

      Ditch the Haynes/ Chilton stuff. Go to MyMopar and download the 71 factory service manual from there and then go to the wiring section and get the aftermarket 2 page wiring diagram. They are not really complete, and don't show all options and connectors, but they are somewhat easier to follow than factory ones "some times"

      If you have ALL the factory electronic components, including the distributor, it can be easily connected. Most folks around here advise against using Mopar electronic simply because modern (current) replacement parts are such poor IE Chinese/ import/ 3rd world quality

      DO you have a what was working ignition system for your engine, that is distributor and whatever else at this time? If so I would CONSIDER tossing that in there at least temporarily before you get into complications.
       
    • Peter J Boncella

      Peter J Boncella Member

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      my 71 harness was working, it is a four point ignition system and i have a HEI distributor will those work together?
       
    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      You can adapt about anything, you are going to have to make some minor changes in the harness no matter what. HEI is a loaded word. What exactly is this?

      If this is an completely integrated "big cap" "looks like a Chevy" HEI then it has one power wire. All you need do is bypass the stock resistor, and hook the original coil wire up to the power lead on the HEI. IF that's what "it is."
       
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