HEI conversion question

Electrical and Ignition

  1. RustyRatRod

    RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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    Did you put some GOOD electric grease compound there? Maybe also add a heat sink between the motor plate and module. Wouldn't hurt. They normally have a heat sink everywhere else.
     
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    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      Don't forget, GM dist's get pretty darn warm, as well. You normally cannot put your hand on the thing for very long when it's been running on a hot summer's day. It would be interesting to know just what that temp is, and or what these modules (original design) can tolerate.
       
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      • 67Dart273

        67Dart273 FABO Gold Member FABO Gold Member

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        What I see there that is a "watch out" is that you seem to have the pickup leads from the dist run VERY close to the plug wires. There is a length limit on pickups, although slant sixes were pretty long, and you need to run the pickup (and other sensor wires) near a ground plane.
         
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        • 71GSSDemon

          71GSSDemon Well-Known Member

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          Yes, I put a lot of the heat sink compound on the back. I have not added a heat sink as i have not experienced any issues even in 90 degrees. Right now I am running without a hood, not sure if that makes a difference. I may have to look further before Mopars in the Park. That will be the longest drive thus far and will have a hood and snorkel scoop on. It does have full air flow from the fan too though.
           
        • RustyRatRod

          RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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          I think Del has a really valid point about running the wire near the plug wires. You might ought to think about rerouting them or maybe shielding.....or even perhaps making that "run" shorter. It could make a difference.....or maybe not. lol
           
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          • 71GSSDemon

            71GSSDemon Well-Known Member

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            I will definitely look at the way the wires are run. Car is sleeping right now at a friends for the winter. Thanks for the great suggestion guys.
             
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            • Bewy

              Bewy Well-Known Member

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              Couple of comments.
              - p/up wires can be quite long & small gauge, as the current & voltages involved is very small.
              - as others have said, keep the wires away from HT leads AND from the coil [-] wire where the back EMF can reach 250+ volts.
              - twisting the p/up wires & keeping them close to a ground plane is a good idea. A better idea is to use screened cable like microphone; ground one end of the screen. I use MC cable as my ign system is mounted under the dash to keep it cool.
              - you cannot have a heat sink that is too big, but you can have one that is too small..
              - the original white heat conduction paste used to transfer heat to heat sinks contains beryllium which is known to be cancerous. There is now a silver paste with silver in it which transfers more heat as silver is an excellent conductor of heat & electricity.
               
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              • 67Dart273

                67Dart273 FABO Gold Member FABO Gold Member

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                That is not a true statement. the low current/ voltage if anything is why you want to keep them SHORT. Pickups / other/ more modern sensors use small current/ voltage and are susceptible to outside electromagnetic fields. There is a well known problem with such as MSD "triggering itself" AKA the power in the plug wires induces a trigger back into the pickup wiring.

                You want to design the layout so the pickup wiring is short, and laid down near a ground plain. Twist the wiring if possible. Use shielded wire and or twisted pair similar to CAT-5. Ground only one end of the shield IE the module end, and insulate the other end, "Faraday shield."

                Certain types of plug wires AKA the old solid core can increase power and magnetic field / radiation from plug wires. It's not just about "radio noise" It's about EMI/ RFI into other sensitive circuits
                 
              • Bewy

                Bewy Well-Known Member

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                Sorry Dart, what I said is very true & 100% correct. The pick up wires can be several feet long, as long as they are kept isolated from magnetic fields, as I described in post 32. You just repeat in post 33 many of the things I already noted in post 32.
                I have on numerous cars installed elec ign systems using magnetic p/ups. One car I did about 10 yrs ago has a rear mount dist & the module is at the front of the car, behind the battery, to keep it cool. P/up wires are twisted, laid along the inner fender, several feet long, zero problems.
                MSD say it is OK to lengthen the wires for it's ign boxes.
                 
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