HEI Coil- E-core vs canister

Electrical and Ignition

  1. mopowers

    mopowers Well-Known Member

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    I'm in the middle of an HEI conversion and need to buy a coil. Are there any canister coils that equal performance of an e-core coil? I've noticed pertronix makes an epoxy filled canister coil with low resistance (0.6 ohm, I believe). Would this work as well as a proper e-core type?
     
  2. TrailBeast

    TrailBeast Slightly Twisted Member

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    They are kinda close, so if that's what you want then go for it.
    The E core coils put out an average of 4-5k volts more energy than the Blaster series round coils.
    I seriously doubt you cold ever tell the difference.
     
  3. mopowers

    mopowers Well-Known Member

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    Thanks for the reply. I was thinking purely from an ease of installation standpoint since they would simply install in the same location as the coil I have now. Then, I started looking and found these epoxy-filled canister coils that have anywhere from .3-.7 ohms primary resistance. They even have 45,000 max voltage. Since I don't know a whole lot about coils and their specs, I'm wondering if one of these would be equivalent to a e-core style coil. Are there any other specs to be concerned with beside primary resistance and max voltage? Would either of these contradict the point of going with HEI in the first place?

    https://www.summitracing.com/parts/msd-8222

    https://www.summitracing.com/parts/pnx-45111
     
  4. BillGrissom

    BillGrissom Well-Known Member

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    Look for KitCarlson's posts which discuss this. I think he would agree that the max voltage spec isn't that significant since it doesn't directly relate to the energy per pulse. The primary resistance probably relates more to energy since lower resistance is more current at dV = 12 V to charge the coil and energy = current * dV. I think the max voltage is important in telling how wide a gap the spark can jump. That is harder at high cylinder pressure, i.e. WOT at low rpm, which is where you might first experience spark miss, and why turbo engines usually spec a smaller spark gap. With a good ignition system, you might be able to run 60 mil spark gap without missing.
     
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    • KitCarlson

      KitCarlson Well-Known Member

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      An E-core coil has an improved magnetic circuit path. The canister coil magnetic path is a rod, so it is like a bar magnet. The E-core wraps around and has a small air gap, so there is less leakage inductance. The E is shape of core, the windings go on the center bar, that is slightly shorter than ends. An I bar closes the ends, the air gap is in the center. The windings, often on a bobbin, are shorter, and fewer turns, less resistance, so less copper losses. So the E-core is more efficient, a higher percentage of energy gets to plug.

      E-core coils are not oil filled, they are in a potted plastic housing. Dwell needs to be properly controlled, by time/current limit. An HEI ignition has that built in.
       
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      • TrailBeast

        TrailBeast Slightly Twisted Member

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        Neither is really equivalent to the Ecore coils, but out of those two canisters I would opt for the second one.
        One of the really good reasons for going HEI is for the reliability of the UCU over the older Mopar units.
        The spark voltage is actually a secondary concern.
         
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        • mopowers

          mopowers Well-Known Member

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          Thanks for the input guys. It sounds like i'm better off getting a true e-core coil. Has anyone used this one? Would it work well with HEI?

          https://www.summitracing.com/parts/msd-8207

          Since it's so small, it seems like mounting it in the stock location would be a piece of cake.

          5878132-MSD.jpg

          AR307aP1.jpg
           
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