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Overdrive kickdown with HEI

Discussion in 'The Hokey Ass Message Board' started by dirty old man, Feb 23, 2014.

  1. dirty old man
    Joined: Feb 2, 2008
    Posts: 8,912

    dirty old man
    Member Emeritus

    Posting this for a friend who is not computer literate, but is as much a hot rodder as any of us. The pickup is a '64 Chev.
    Truck is one he's installed an OD Chev. trans., a late model 3 spped synchro 1st gear, but Borg Warner od controls are pretty much the same all the way back.
    Book says hook kickdown wire to negative side of coil in order to interrupt power to allow od to kick down.
    But an HEI ignition has no "negative wire" on the coil. He asked me to do some research for a solution, so here I am, checking in and asking the biggest data bank I know of for some help.
  2. dirty old man
    Joined: Feb 2, 2008
    Posts: 8,912

    dirty old man
    Member Emeritus

    Thx for the link, but most of the discussion there was about Pertronix or Mallory Unilite, both of which still use a seperate coil, whereas the HEI uses an tntegral coil with no "negative terminal". Nobody in that thread directly had experience with this on an HEI.
    GMC Bubba, where are you?
  3. saltflats
    Joined: Aug 14, 2007
    Posts: 11,259

    from Missouri

    Wont the tach terminal on the cap be the neg side of the coil.

  4. tfeverfred
    Joined: Nov 11, 2006
    Posts: 15,792

    Member Emeritus

    Doesn't Ron Francis make a kit to set it up to work off a switch? If they do, maybe the instructions would help him.
  5. Best way to do this and retain full OEM function would be to use the original kickdown relay to drive another relay and use that one to interrupt power to the ignition rather than short it to ground. This method should work with any electronic ignition.
  6. Jeff Walker
    Joined: Feb 6, 2007
    Posts: 498

    Jeff Walker

    I did the same swap several years ago on a 66 GMC with a 350 and HEI. I hooked the wire that went to the neg side of the coil for the kickdown to the tach terminal and it worked fine.

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  7. stimpy
    Joined: Apr 16, 2006
    Posts: 3,547


    the wire feeding the tach connector side of the coil is the one you hook too . its yellow or brown . should be labeled c-

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