troubleshooting question? 1968 350 running rough

Discussion in 'The Bench' started by Max Damage, Sep 10, 2020.

  1. Max Damage

    Max Damage I'm thinking about it!

    I have been working on my 68 GS California car, as my daughter has just turned 16 and likes to drive away with my daily driver.

    Despite some minor issues (Brakes?) the car has been running perfectly. Yesterday I went to use it for a quick trip to the supermarket and the car started right up, but when it came off high idle, it ran rough (missing). I was able to nurse it to the market and then back home, but today it is the same.

    As I said the car was running great, and nothing has changed or been worked on. It seems to me that there is excessive black smoke (too much fuel) coming out my left tail pipe. Also after shut down, I hear a gurgling from the carb and there was a little wafting of smoke from the carb as well?

    I am interested in the best approach to troubleshoot this and ideas on what has gone wrong. The car still starts immediately and runs. It did sit for years before this recent round of love.

    Thanks in advance for ideas and tips.
     
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Are you running the same gasoline that the car sat with for years?
     
  3. gsgnnut

    gsgnnut Well-Known Member

    classic dirty carb symptom. blow out the jets with compressed air/carb cleaner it will probable be fine.
     
  4. gsgnnut

    gsgnnut Well-Known Member

    especially if there were a few spirited romps on the way to the market. :D
     
  5. BuickV8Mike

    BuickV8Mike SD Buick Fan

    The best approach is simple.....Follow Larry's advice. lol
     
    Oldskewl59 likes this.
  6. Max Damage

    Max Damage I'm thinking about it!

    No the Gas isn't that old. I generally fire the car up several times a year at minimum and roll it around a bit. 1/2 of the gas might be 3 years old, the rest is new Alcohol free premium with a couple of cans of techron in it.

    Spraying some carb cleaner sounds possible. I do have another whole car (GS400) that I could sip the carb from as a test...
     
  7. yachtsmanbill

    yachtsmanbill Well-Known Member

    Run a fingernail file over the points "while yer in there". ws
     
  8. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    I'd never have gas that was 3 years old in my tank. It won't last that long no matter what you put in it. Beyond that, I would certainly check all the basics. Check the point condition, dwell, distributor cap and rotor, wires and spark plugs. Put a vacuum gauge on it, and look for vacuum leaks if it is low. Carburetor mounting gasket and all vacuum hoses.
     
  9. Max Damage

    Max Damage I'm thinking about it!

    Ok, just to follow up. Digging around I found multiple things wrong. Using a timing light I could see that when the car first started, still on high idle the plugs all looked to be firing ok, but when the car went to low idle the firing degraded and got worse over time. Pulled the plugs and they looked fouled. Also, when the plugs fouled I could see arcing at several.

    1) Alternator belt was not tight. Seems that at idle it wasn't turning fast enough. It's the old standard externally regulated model.
    2) Replaced all Plugs with the NGK 04 that Larry recommended elsewhere.
    3) Replaced the Ignition wires with Blue Streak
    4) Pulled carb and had it rebuilt at Edmonds Auto and Marine (Travis)

    According to Travis, float was not working correctly and bowl plugs were leaking (classic).

    Today I finally had time to work on the car. Swapped out the plugs, installed the new wires, and reinstalled the carb. Also changed the fuel filter while it was disconnected.

    Car fired up and runs SUPER. I know I said the car was running well before, but I was wrong ;~)

    Thanks for all of you help!
     

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