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tach hookup with HEI?

Discussion in 'The Garage' started by Jonny-K5, Apr 8, 2004.

  1. Jonny-K5

    Jonny-K5 1/2 ton status

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    i know this has been posted before but i dont have time to search. what wire to you hook up to? my 89 has its own tach lead, but this 70's HEI im working with doesnt have any provisions for one. do i cut and splice? which wire is the negative coil wire?thanks
     
  2. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    The dist cap has a square section that pokes out, the main ign wire connects here. Look closely and you'll see "tach" on the terminal next to it.
     
  3. Jonny-K5

    Jonny-K5 1/2 ton status

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    my truck has two wires connected to that square box. i thought both were hot ignition wires. are there more than two connections? does the ignition only run on one wire? ive looked closely for markings, i'll have to check again.
     
  4. gm4x

    gm4x 1/2 ton status

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    I just put a set of wires on my 86 305 powerhouse ( /forums/images/graemlins/histerical.gif) and recall seeing the "tach" marking, I think is on the wiring connector. If I recall, mine only has 1 wire, but it plugs into an adapter of sorts that only uses 1 of the "ports", before plugging into the cap. So I still have an open connector for tach (since I don't have one). Pop out your connector & see if you can find the marking there.
     
  5. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    Yeah, it only needs one for ignition. You should have 2 wires in a common plug that go from the dist base into the block closer to the cap. Next you should have a single with with a plug that goes into the block where it's marked "ign". There should be an unused corner of the block marked "tach" that will accpet an OE plug (like on the ign wire) or a female blade type wire connecter.
     
  6. Jonny-K5

    Jonny-K5 1/2 ton status

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    just looked at the dist. again. i see the markings, one tach and one batt. i was looking on the side of the box when its marked on the top. i wonder where that wire goes that was hooked up to the tach goes to. thanks for all the replys fellas. /forums/images/graemlins/thumb.gif
     
  7. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    Maybe the previous owner had a tach in the truck? I know of no other purpose for using that terminal.
     

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