364 runs rough intermittently?

Discussion in ''Da Nailhead' started by 67NorCalGS, Apr 24, 2019.

  1. 67NorCalGS

    67NorCalGS Well-Known Member

    It's about a 70/30 split. 70% of the time it runs very smooth. Then randomly I have an idle drop and runs rough. After awhile it goes away. It may run good the entire drive. Then happen the next time. Been this way for years. Was wondering if it could be a sticking valve or maybe faulty lifter? The ignition system is all new minus the coil and distributor.
  2. PGSS

    PGSS Well-Known Member

    Did you notice it ran worse when the weather was hot or raining or drizzle?
  3. 67NorCalGS

    67NorCalGS Well-Known Member

    I need to pay more attention I guess. I can't really detect any pattern.
  4. 1972Mach1

    1972Mach1 Just some guy.....

    What are you running for a carb? Maybe a possible vacuum leak, check the throttle shaft for play. Especially on Quadrajets, the shaft bushings can wear out and they'll run just dandy and then start sucking air and lean out. When it runs rough, start spraying either WD-40 or Brake Cleaner if your engine isn't detailed around the base of the carb, intake ports, throttle shaft, vacuum booster, etc. Anywhere that has vacuum going to it. If the idle changes, you've found a leak.
    67NorCalGS likes this.
  5. 67NorCalGS

    67NorCalGS Well-Known Member

    Hey thanks, I knew that trick at one time. It's a two barrel Stromberg. I'll give it a shot. I did change the carb about ten years ago. I still have the old one.
  6. pbr400

    pbr400 68GS400

    It sounds like an intermittent vacuum leak to me, too. I have a qjet with a slight warp to the surface between the body and bottom; it would act like that. Using a better gasket seems to have fixed it.
  7. 67NorCalGS

    67NorCalGS Well-Known Member

    I remember one of the carbs was warped pretty bad. I'll definitely check that next.
    1972Mach1 likes this.

Share This Page