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Technical The fantastic mystery of the great engine gremlin(318 Magnum "misfire")

Discussion in 'The Hokey Ass Message Board' started by Flooganbargan, Nov 25, 2022.

  1. Flooganbargan
    Joined: Jun 14, 2015
    Posts: 60

    Flooganbargan
    Member
    from Tennessee

    I ran the ground wire to the distributor to make sure it had a proper ground and wasn't grounding out only through the intermediate shaft or anything. 318 distributors have o-rings instead of gaskets, and there's a thick coat of paint on the engine. But it seems it's getting adequate ground afterall.

    When I ran a direct hot wire from BATT + to the distributor, it was with the HEI chevy style 1 wire installed.

    As for the plugs, I'll clean em up. They're brand new with the motor, so I don't see how they could be bad beyond just being 'fouled'. Like I said, they're not oily nor particularly sooty, just black-ish and all uniform to one another.
    I'll do just that. I forgot about that trick.

    There's no symptoms I can think of that would manifest in both an HEI electronic dist as well as a points dist in the same exact way, unless I'm the most uniquely unluckiest guy in the universe(a distinct possibility).

    It is indeed. Checked with a multimeter when the HEI was in. There's only one tenth of a volt difference between the battery and the ignition positive lead. All the other wiring for the points dist is brand new.

    I'm going to order a different style coil tonight. One with a ballast built in. This seemingly ignition related problem is running out of ignition related causes really fast. I'll update when I get the new points, condenser, and coil in, though I have my doubts I'd like to have the spares anyway.
     
    Last edited: Nov 26, 2022
  2. Moriarity
    Joined: Apr 11, 2001
    Posts: 26,405

    Moriarity
    SUPER MODERATOR
    Staff Member

    so, if it ran better with an open vacuum line and the plugs are black, I bet it is an over rich condition. I know that you tried 3 carbs, but what if the fuel pump has malfunctioned and is putting out too much psi forcing the needle off the seat and flooding it? check the fuel pump pressure. I had a bad one on my impala this summer and the mech pump was making 10 psi!!
     
  3. Flooganbargan
    Joined: Jun 14, 2015
    Posts: 60

    Flooganbargan
    Member
    from Tennessee

    I'll test that tomorrow. Thank god my vacuum gauge is dual purpose.
     
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  4. BJR
    Joined: Mar 11, 2005
    Posts: 8,021

    BJR
    Member

    You have a bisexual vacuum gauge?:eek::D:p
     
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  5. southerncad
    Joined: Feb 5, 2008
    Posts: 847

    southerncad
    Member

    OK, I'll go the other way from everybody else...could it be a fuel problem? Contaminated with water/condensation, just plain old/bad or junk floating around in the tank that gets picked up sometime? Be sure to let us know what fixes the problem.
     
    Flooganbargan likes this.
  6. garyf
    Joined: Aug 11, 2006
    Posts: 256

    garyf
    Member

    Worn valve guide or egr valve unseating and then seating ?
     
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  7. King ford
    Joined: Mar 18, 2013
    Posts: 1,476

    King ford
    Member
    from 08302

    Is your aftermarket cam the same firing order?….is your intake manifold single plane or dual plane??….if you don’t have access to an igniter “scope” hook up a timing light , stick it under th windshield wiper and take a ride…watch the flash pattern…make sure your exhaust pipes are open….no mice nest or any blockage….some exhaust pipe is double wall and the inside pipe can collapse causing a serious blockage….
     
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  8. Flooganbargan
    Joined: Jun 14, 2015
    Posts: 60

    Flooganbargan
    Member
    from Tennessee

    Wow.

    I replaced the coil with a brand new one, cleaned up the points while I was under there, and the old symptoms went away. Engine runs smoothly below 2,500RPM. New problem: it breaks up at anything beyond 2,500RPM and feels like I have a 2step rev limiter installed at 3,000 RPM.

    So out of 4 coils I tried, one relatively new HEI accel coil(less than 500 miles on it! It came from the LA block), one HEI master pro coil(brand new in box, bought last year and sat on my shelf as a backup), one accel super stock coil(used), and one standard motor products coil(brand new in box), ALL OF THEM WERE BAD. Three being bad in the same way, and the brand new one being bad in a different way. I DID triple/quadruple check the ignition wiring.

    So I suppose I'm on a quest to find a decent ignition coil now.

    Thanks to all who've helped. Either I'm the unluckiest guy in the universe, or they really don't make them like they used too. Sheesh.
     
  9. Flooganbargan
    Joined: Jun 14, 2015
    Posts: 60

    Flooganbargan
    Member
    from Tennessee

    Bang on the money, only it happened to me 4 times in a row.
     
  10. That is weird!! I have owned 25+ cars in my time and had exactly ZERO [0] bad coils. On the other hand, there have been numerous rotors, caps, wires, etc. go bad.
    Good luck

    Ben
     
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  11. greybeard360
    Joined: Feb 28, 2008
    Posts: 2,022

    greybeard360
    Member

    I got a voltage regulator from AZ once... Eckler brand... for a Mopar. It wouldn't charge. I took it back and they tested it... No good. He pulled another one off the shelf and tested it... No good. None of the 5 others he had worked either. I ended up buying a Borg Warner and it tested good and fixed the car. Some times you do have to spend a little more for better quality.
     
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  12. dalesnyder
    Joined: Feb 6, 2008
    Posts: 563

    dalesnyder
    Member

    Under the coil cover on an hei distributor is a ground strap.. make sure it’s there.. every bad coil on an hei I have seen was missing that strap.
     
  13. I dunno ... I ain't convinced :(
     
    firstinsteele and Flooganbargan like this.
  14. Flooganbargan
    Joined: Jun 14, 2015
    Posts: 60

    Flooganbargan
    Member
    from Tennessee

    OK, I might have been a little hasty on the new coil. I replaced the points and condenser inside the distributor and the motor runs all the way to 5 grand now. Oops. :oops:

    I have had two HEI coils on two Chevys go bad on me. Specifically their power wires melting. One during a very long highway trip, the other seemingly randomly after about 10 minutes on the highway in a separate vehicle. It's why I switched to accel coils. I figured it was just the cheap coils.... Ive always liked HEI dists because of their wiring simplicity, but I think I'm just going to convert to points. From here on.


    I do make sure they've got that strap.
     
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  15. Moriarity
    Joined: Apr 11, 2001
    Posts: 26,405

    Moriarity
    SUPER MODERATOR
    Staff Member




    OK wait just a minute, This is a conventional points ignition? I think we somehow had the idea that
    it had an HEI distributor in it. anyhow congrats on getting it going, sounds like it was the points or condenser all along.
     
    Flooganbargan likes this.
  16. Flooganbargan
    Joined: Jun 14, 2015
    Posts: 60

    Flooganbargan
    Member
    from Tennessee

    It started out as HEI, I swapped over to a brand new points distributor after failing to pin point the issue.

    I know I write long ass novels for posts so I don't expect everyone to read through it all. I just can't help it.
     
    tommyd and Moriarity like this.
  17. BJR
    Joined: Mar 11, 2005
    Posts: 8,021

    BJR
    Member

    Thanks for getting back and posting what fixed it.
     
    G-son likes this.
  18. Budget36
    Joined: Nov 29, 2014
    Posts: 10,435

    Budget36
    Member

    One of the wires on my ‘78 Camaro did the same thing, melted through and was shorting out. This was in ‘81/‘82. Only HEI I ever had that had an issue
     

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