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Technical HEI input voltage

Discussion in 'The Hokey Ass Message Board' started by Hotrodjohn71, Nov 22, 2022.

  1. Hotrodjohn71
    Joined: Feb 25, 2018
    Posts: 130

    Hotrodjohn71

    How low of an input voltage will an HEI setup tolerate? And what would be the immediate effects of a voltage dropping below that threshold?
    On my engine, it appears that my alternator is not doing very well anymore and at idle, the voltage drops to right around 12 volts. I have an HEI setup and at idle it has misfire. But when I rev up the motor and the voltage Rises back up around 13 to 14, it runs good. So I'm trying to determine if it might be a voltage shortage to the HEI before I start tearing into it and look for fuel supply issues or something else.
     
    Last edited: Nov 22, 2022
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 59,180

    squirrel
    Member

    engines with HEI will start when cranking, and the battery voltage is usually around 8-10 volts?

    Misfiring seems to be the result of running low on power at higher rpm, though. When cranking, there's lots of time for the system to "charge" between firings, not so at higher RPM.
     
    hrm2k, jaracer, Hotrodjohn71 and 2 others like this.
  3. NoelC
    Joined: Mar 21, 2018
    Posts: 667

    NoelC
    Member

    HEI Distributor Troubleshooting With Performance Distributors (chevyhardcore.com)

    Well, I think Hotrodjohn71 you need to ask yourself, if you're going to ask the doctor over the phone about your condition with hopes of getting a solid response that proves beneficial, you might want to give as much back history as possible to cure the condition not just treat the symptoms.

    I think it's a fuel pump issue.
     
    Hotrodjohn71, hrm2k and squirrel like this.
  4. Driver50x
    Joined: May 5, 2014
    Posts: 540

    Driver50x
    Member

    I doubt that is the problem. If you want to make sure, just hook up a battery charger while the engine is idling and see if that changes anything.
     
    BJR, VANDENPLAS, G-son and 1 other person like this.
  5. Illustrious Hector
    Joined: Jun 15, 2020
    Posts: 571

    Illustrious Hector
    Member

    Load tested the battery?
     
    VANDENPLAS and Hotrodjohn71 like this.
  6. Ahhhh …. Maybe . But probably no .

    Vacuum leaks ?
    Age of tune up ?
    Fuel filter ?
    Stuck / sticking vacuum advance / fly weights ?
    Bad ground or wiring ?
    Coil ?
    Carb ?
    Fuel pressure ?
    Lager or ale ?


    Could be a multitude of things , easy to check th off the list . Even easier to point the parts canon at it and blow some dough on a simple fix .


    I spent a day checking stuff on my ford 302 for a no start , ended up being a missing spring clip on the distributor .!!
    Point is don’t overlook anything , no matter how stupid you may think it is .
     
    Hotrodjohn71 likes this.
  7. jimmy six
    Joined: Mar 21, 2006
    Posts: 16,653

    jimmy six
    ALLIANCE MEMBER

    Battery analysis electronic tools are very reasonable now and a life saver.
     
    Hotrodjohn71 likes this.
  8. Hotrodjohn71
    Joined: Feb 25, 2018
    Posts: 130

    Hotrodjohn71

    Thanks a million guys. Let me use what you've given so far and I will check back in. Thank you
     
    Driver50x and NoelC like this.

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