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GM Wiring - HEI Hook-up ---HELP!!!

Discussion in 'The Hokey Ass Message Board' started by Chopped50Ford, Mar 25, 2005.

  1. Okay, i dont know if this has been covered, but Im doing a motor swap from an 87 Chevy for a 54 Plymouth. The motor is a 5.0 liter 305 w/ 700r4 trans behind it.

    I have a few questions on this motor, Im hoping to fire it for the first time in the car tomorrow.
    1. How do you install HEI distributor in this SBC? I understand you drop it in, but do you have to set the firing order to #1 cylinder? How do you tell?..What is the firing order on the cap for the wiring, to the plugs? There are 2 wires on the HEI, what do they get hooked to? I believe someone told me one is for tach, the other constant power (with key in the "on" position in the ignition)

    2. Alternator - okay, its got the large wire on the battery cable but smaller, and this 3 prong plug on the ("drivers) side of the unit. There are 3 wires in the plug. I read that those wires are not needed, only the "battery-like" cable is used and hooked directly to power to battery for charging. I believe its a "One wire" alternator.

    3. Does the battery hook directly to the starter? or daisy chain from the alternator. example: battery cable from postitive post to alternator hookup then to starter.

    4. Ground strap/cable. The battery ground goes to the block. then a ground strap to the frame. Where is a good spot for the ground to go on the block?

    Thanks for the help in advance. I hope to have this thing purring by evening. Maybe the car could have a possibility to make Viva!!!
  2. Snake9t9
    Joined: Dec 30, 2001
    Posts: 140


    To drop the distributor in, bring the motor up to TDC on #1 cyl. The distributor cap should be marked for the #1 cylinder, all the ones I have are.

    There should only be two terminals on the dist. One is for the tach the other goes to a key on 12v source.

    I always run the ground strap from the frame to an empty bolt hole on the back of the cylinder head
  3. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,707

    Fat Hack
    from Detroit

    Here is a simple drawing that shows how I typically wire GM engines with electronic ignition (HEI) distributors and the 70s/80s era internally regulated alternators.

    (Note: The small red wire going from the alternator to the key switch jumps over the wire it crosses in the diagram, it is not spliced in).

    1. Run your main (+) battery cable from the battery to the large stud on the starter solenoid.

    2. Run a 10ga wire from the output stud on the alternator to the same stud on the solenoid where the battery cable is hooked to in step 1.

    3. Run a 10ga or 12ga wire from the 'cranking' position on the key switch to the smaller stud on the starter solenoid.

    4. Run a 12ga or 14ga wire from the 'ignition' position on the key switch to the 12v ignition lead on your coil, located on the distributor cap. No resistance is used in an HEI application.

    5. Run a 12ga or 14ga wire from the 'exciter' (red) wire on the alternator plug to a keyed 12v power source. I use the 'accessory' position on the key, but some guys just loop the exciter wire over to the output stud on the alternator...your choice.

    As far as ground wires go, you can't OVER ground your car, so I go kinda overkill here, but it makes for a 100% reliable and trouble free electrical system. Here's my method:

    1. Run the main negative (-) cable from the battery post to a point on the engine block near the starter. I tend to use a bellhousing bolt in most cases.

    2. Obtain a Ford type 'switch to starter' cable and connect that from the point where the negative cable meets the block (or trans) to the firewall using a 3/8" bolt or stud.

    (A Ford 'switch-to-starter' cable is a battery cable with a ring loop at each end, in a typical Ford application, it goes from the relay on the fender down to the starter. Most places carry these cables in black as well as red, and in various lengths to suit your needs. Buying a black one eliminates any confusion with the positive (often red) battery cable.)

    I used solid steel motor mounts on my car, so another cable or strap from the body to the frame was not required...and also because I grounded all electrical components to the stud on the firewall where the ground cable hooks up, so nothing is grounded to the frame.

    However, a flat braided ground strap going from some point on the engine block to your frame rail is a good idea if you use rubber insulated motor mounts and want to be sure that your frame is grounded.

    (Of course, it goes without saying that all your connections need to be clean...scrape any paint or rust off where ground wires attatch, and use No-Ox-Id or some other weatherproofing electrical compound to insure good conductivity for a long, long time.)

    Hope this helps you out!
    David R. Smith likes this.
  4. Don't forget the fusable links or maxi fuses ;)
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  5. blackanblue
    Joined: Feb 20, 2009
    Posts: 292


    lots of good info, good luck on the first start i'm about 3 weeks behind you with my 52 gmc.
  6. L
    Lmao !!!
    Three weeks behind

    Nine year old thread
    3 months short of 10 years
  7. harpo1313
    Joined: Jan 4, 2008
    Posts: 1,307

    from wareham,ma

    Ya,but the search function works good,

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