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How do you tap into

Discussion in '40- & 55-Series Tech' started by ScottFJ40, Mar 25, 2003.

  1. ScottFJ40

    ScottFJ40

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    the fuse box for a power supply. I am looking for a 12v power supply for my hei. How do you guys tap into the fusebox. Sorry for the noobish question, I am an electrical moron. :D
     
  2. Pin_Head

    Pin_Head

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    Best way would be to run it off the stock key-on "engine" fuse circuit. This circuit is the wires that are black with a yellow stripe that originally ran to the coil, idle solenoid, VSV, etc.
     
  3. Vortec_Cruiser

    Vortec_Cruiser

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    Your fuse block will have two male spade fittings on the front side. One is for keyed-power, and the other is constant power. You may have to unbolt the fuse block from the pillar to see the fittings. ::)
     
  4. woody

    woody Internet Fireman Staff Member

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    I've used both of those spade fittings for external fuse blocks with great success....

    But the black/yellow stripe wire is what connects to your HEI coil input. This is not only run-hot but also start-hot, which is important.
     
  5. Webster

    Webster

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    When you say start-hot you mean while cranking,correct?
    I am doing a TBI conversion and am trying to find the correct wire that is hot while on/running/cranking.
     
  6. woody

    woody Internet Fireman Staff Member

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    yeppers....hot while cranking....and that's the black-yellow wire in the Cruiser harness.

    See the tech section/Chev swaps for some TBI 350 wire diagrams I just linked up today....
     
  7. ScottFJ40

    ScottFJ40

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    Thanks once again guys for your comments and suggestions. I have to buy a multimeter I guess.
     
  8. Degnol

    Degnol

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    Scott,
    Another suggestion would be to use your existing ignition-on wire in the stock loom and instead of running it straight to your HEI (it's too small) run it to a 30 amp relay that draws it's power straight from the battery. Then run a 10ga wire from the relay to the HEI. The HEI calls for a 10 ga wire. However I did wire mine direct, with no problems....yet. But I plan on wiring in the relay.
    I'm still a "Rookie" so somebody please grade my paper. Seriously
    Ed Long
     
  9. woody

    woody Internet Fireman Staff Member

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    I did the relay on my carbed 350 for a while...there was no seat-of-the-pants difference at all. On my TBI350 install, I just used the wire direct.
     
  10. 72cruiser

    72cruiser

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    hey guys,

    i just finished my HEI (and in a hurry so i could actually go home over spring break, ha ha). i haven't done the fuse/relay thing yet.

    could someone explain to me how and why for this? i'd be real grateful, esp. b/c i have no electrical experience whatsoever.

    thanks,
    jonathan
     
  11. Degnol

    Degnol

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    Like I said, no problems with it wired direct, yet, but my experience with automotive wiring is, the bigger the better, with the appropriate fuse and/or relay. I don't think it is as much a performance issue as it is a safety issue. If GM calls for a 10ga wire, believe me they're not going to specify a wire any larger then necessary. IMHO
    Ed Long
    I hate electrical fires, they're so very....well...stinky and they fry a lot of sh*t