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What ignition coil to use?

Discussion in 'The Hokey Ass Message Board' started by Gus68, Feb 6, 2014.

  1. Gus68
    Joined: Jan 29, 2007
    Posts: 374

    Gus68
    Member
    from Minnesota

    Hey guys!!! Been doing some searching and now I'm even more confused than I was before. Here is what I have. I have a 350 chevy and a 4 speed (if that makes any difference). My distributer is a stock points style that I modified to fit a Chrysler reluctor wheel and electronic pickup, and I am going to use an MSD 6AL box. Sooooo..... What do I use for a coil? And do I need to resist the power wire? Also is there any good coils from NAPA or CARQUEST? It seems that a lot of things now a days are made by the same company. But I will go with an MSD or another brand if they are better. Thanks for reading my ramblings!!!!
     
  2. GMC BUBBA
    Joined: Jun 15, 2006
    Posts: 3,358

    GMC BUBBA
    Member

    the IC12 coil from napa is very good ............
     
  3. Bent Wrench
    Joined: Jun 18, 2009
    Posts: 19

    Bent Wrench
    Member

  4. Gus68
    Joined: Jan 29, 2007
    Posts: 374

    Gus68
    Member
    from Minnesota

    Does the NAPA IC12 need a resistor in front of it?
     
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  5. Gus68
    Joined: Jan 29, 2007
    Posts: 374

    Gus68
    Member
    from Minnesota

    Anyone????
     
  6. brokenspoke
    Joined: Jul 26, 2005
    Posts: 2,874

    brokenspoke
    Member

    correc me if i'm wrong.....a resister is only needed using points
     
  7. nailheadroadster
    Joined: Jun 7, 2006
    Posts: 1,523

    nailheadroadster
    Member

    Thats what I thought also.
     
  8. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    hoop98
    Member
    from Texas

    The coil is 1.5 ohms so will flow 8 - 9 amps when saturated. I would use a 1.2 - 1.5 ohm ballast resistor. The MSD can handle the current but the coil will run hotter without the resistor.
     
    Last edited: Feb 10, 2014
  9. Gus68
    Joined: Jan 29, 2007
    Posts: 374

    Gus68
    Member
    from Minnesota

    I thought it was only needed for points also. But the more I read the more I get confused!:confused:
     
  10. brokenspoke
    Joined: Jul 26, 2005
    Posts: 2,874

    brokenspoke
    Member

    Hopefully GMC Bubba will respond
     
  11. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    hoop98
    Member
    from Texas

    That is a 6V coil I believe. I am sure the MSD can handle the current but I would be concerned about the coil running hot, maybe Bubba has run that combination before. It will obviously run without a resistor but without a current limiting module you will be running the coil t twice it's normal current. Their are low resistance ballast resistors down around the 1 - 1.2 ohm range which will limit the current at low speeds then allow more current at high rpm.

    If you run it without a resistor check the coil temperature at idle. If it gets too hot to touch you will probably


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  12. joel
    Joined: Oct 10, 2009
    Posts: 1,557

    joel
    ALLIANCE MEMBER

    When you use the MSD box, the distributor is just a trigger. The dist. connects to the box and the box fires the coil. I would defer to Bubbas suggestion .or use the recommended MSD coil.
     
  13. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    hoop98
    Member
    from Texas

    I found info that says the IC12 coil is 2.1 ohms and is used on 6 or 12 volt. It will probably work without a resistor. If it runs hot MSD has a .8 ohm resistor. That would make the coil carry a little over 4 amps. The MSD box can carry plenty of current it's not the weak link.

    So try it with no resistor, if it runs too hot use a low resistance like .8.

    Hoop
     
  14. sunbeam
    Joined: Oct 22, 2010
    Posts: 4,539

    sunbeam
    Member

    Chrysler used a resister with electronic ignition.
     
  15. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    hoop98
    Member
    from Texas

    Breaker Points can only handle 4-5 amps without premature wear.

    So they used a total of about 1.5 ohms coi resistance (12 Volt) and a "ballast resistor".

    A ballast resistor is dynamic, meaning it has high resistnce at idle and low rpm and less after abut 3,000 RPM when the coil cannot reach full current.

    This helps keep the points alive.

    HEI limits the current in the module to about 5.5 amps, it uses a low resistance coil to reach higher current and charge faster.

    MultiSparkDischarge fires the plugs multiple times at idle until it runs out of charging time.

    The coil will let you know if it is handling too much current by getting hot, overheating, or shutting down, or melting.

    That would depend on the severity of the problem.

    Hoop
     
  16. fsae0607
    Joined: Apr 3, 2012
    Posts: 870

    fsae0607
    Member

    Don't think you need a resistor. As joel said, the MSD unit will take care of saturating the coil. I have a MSD 6A on my O/T car and IIRC there's two leads (orange/black) going to the coil. You want a full 12V going into your MSD box for the main power lead (the thick gauge wire). The thin gauge IGN wire comes from your key switch and doesn't need a full 12V to keep the MSD unit on.

    Just pick a coil from that compatibility list and run it!
     
    Last edited: Feb 12, 2014

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