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Technical grounding distributor

Discussion in 'The Hokey Ass Message Board' started by speedshifter, Dec 11, 2021.

  1. speedshifter
    Joined: Mar 3, 2008
    Posts: 312

    speedshifter
    Member

    While my hot rod was comfortably idling ( 324 Olds with an aluminum housing W&H ducoil distributor) I connected a jumper wire to the engine block & scratched the wire against the dist. hsg. small blue sparks appeared ! This of course indicated a poor ground at the dist. The engine was running perfectly. I ran a permanent wire to the block. My son says his IMCA friends always ground their HEI dists externally. I'm 81 & still learning. speedshifter Greg White
     
  2. BJR
    Joined: Mar 11, 2005
    Posts: 7,996

    BJR
    Member

    That makes sense, I will have to try the spark test and see if mine are needing better grounds.
     
    loudbang likes this.
  3. Doublepumper
    Joined: Jun 26, 2016
    Posts: 1,260

    Doublepumper
    Member
    from WA-OR, USA

    Yep, battery to frame, engine, body, truck bed, radiator, distributor, alternator, and lots of redundant grounds for lighting and other elect. equipment. It makes a difference, especially on our old heaps.
     
    mad mikey, loudbang and Wanderlust like this.
  4. tubman
    Joined: May 16, 2007
    Posts: 6,303

    tubman
    ALLIANCE MEMBER

    It may be a high tension (secondary voltage) leak. Try it with the engine not running, but the ignition on. Make sure the poinjts are closed.
     
    Hnstray, loudbang and BJR like this.

  5. rockable
    Joined: Dec 21, 2009
    Posts: 4,056

    rockable
    ALLIANCE MEMBER

    I usually tap a hole in the distributor body and with a wire, ground it to the same spot on the firewall as the coil. Nobody ever had a problem with too many grounds.
     
  6. This may or may not be the case, but I remember reading once that the hold down clamp was supposed to form a ground to the block (and then block to frame etc.) This was in the context of paint and so on potentially causing a connection problem.
     
    Hnstray, jimmy six, charleyw and 2 others like this.
  7. Dennis D
    Joined: May 2, 2009
    Posts: 825

    Dennis D
    Member

    I think some of the PerTronix ign. problems could be helped with this idea.
     
  8. rockable
    Joined: Dec 21, 2009
    Posts: 4,056

    rockable
    ALLIANCE MEMBER

    After a Pertronix failure is when I started doing this.
     
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  9. Truck64
    Joined: Oct 18, 2015
    Posts: 5,325

    Truck64
    Member
    from Ioway

    There is an excessive resistance test, to be measured between the distributor points plate and the battery ground post, it's important regardless whether running Ignitor or contact points. Should not exceed 0.2 ohms, the resistance of the meter leads need to be subtracted for accurate measurement.
     
    Driver50x likes this.
  10. G-son
    Joined: Dec 19, 2012
    Posts: 1,098

    G-son
    Member
    from Sweden

    Any time you need an accurate resistance measurment of less than a few ohms you should do a four wire measurment (a.k.a. Kelvin), where you use a separate source to run a known current through what you want to measure, and then you measure the voltage drop across it. Very accurate as the resistance in the meter wires etc. doesn't matter, you just need to know the current going through it all and the voltage across the interesting bits, and calculate resistance using ohms law (R=V/A).

    [​IMG]
     
    Truck64 likes this.
  11. Driver50x
    Joined: May 5, 2014
    Posts: 285

    Driver50x
    Member

    Interesting. Smokey Yunick always recommended an external ground to the distributor.
     
    Truck64 likes this.
  12. Driver50x
    Joined: May 5, 2014
    Posts: 285

    Driver50x
    Member

    You could just connect a volt meter between the battery ground post and the distributor base with the engine running. Ideally it should read zero volts or very close to zero. That is a pretty accurate way to test 12 volt automotive circuits.
     
    rockable likes this.
  13. speedshifter
    Joined: Mar 3, 2008
    Posts: 312

    speedshifter
    Member

    Driver50X I am familiar with the low voltage test. I considered making thar test but I was lazy& the spark test was good enough for me. Greg
     
    Driver50x likes this.

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