70 q-jet choke

Discussion in 'The Venerable Q-Jet' started by BrianM, Dec 21, 2021.

  1. BrianM

    BrianM Active Member

    I have a 70 Riv with a 7040247 carb. Thought I was having carb issues that turned out to be a timing issue. I took the carb to a local shop for a rebuild and now I am having choke issues. Prior to taking it to the carb shop the choke worked almost too well and you had to blip it a few times to get the idle to settle down from a fast idle even when it was 90+ degrees outside. Here we are a few months later and much cooler outside. Now after the rebuild I have to open the air cleaner and tap the choke blade shut for it to work most of the time and when it does work it locks out the secondaries and they may or may not open up after the car warms up.
    The only changes I am aware of was the carb to manifold gasket. The one that came off was about 1/4 thick and the only one I could source locally was the thin standard gasket and carb shop replaced the vacuum canister thing on the primaries.
    Do I need to source the thicker gasket?
    Do I need to adjust bend/play with the choke linkages?
    Take it back to the carb shop and ask them to help?
    I haven't ever worked on a carb with this type of choke and know it worked previously but don't want to just randomly fiddle with things.
    Thanks,
    Brian
     
  2. Max Damage

    Max Damage I'm working on it!

    If the carb has a divorced choke thermostat (in the intake manifold) the linkage that connects it needs to be readjusted (ie bent) to accommodate the new thinner gasket.
     
  3. BrianM

    BrianM Active Member

    Yes one of the choke rods goes to the intake manifold.
    So the thick gasket is what is supposed to be ran on the 455? The one I removed was leaking/damaged but the part number came back as Olds so I wasn't sure. My local part shop listed the thin paper gasket as what was used but they have been hit or miss with Buick parts.
    The rod from the manifold that connects to the choke linkage had more than one hole that could be used on the carb side. Guess I can swap the holes and get a new gasket before I go to bending things.
    Thanks
     
  4. Max Damage

    Max Damage I'm working on it!

    I believe the OEM gasket was thin, but that is just a guess.

    It doesn’t really matter. Just adjust the choke linkage, and you should be good.

    if you think about it the fact the gasket got thinner means the force applied by the choke thermostat is less. The linkage is designed to be bent for adjustment. This is normal.
     
  5. BrianM

    BrianM Active Member

    Thanks will play with it this weekend and see if I can get it working better.
     
    Max Damage likes this.
  6. LARRY70GS

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

    techg8 likes this.
  7. BadBrad

    BadBrad Got 4-speed?

    Trying to remember if I even adjusted the divorced choke drive when I installed a half inch wood spacer; it's probably been 27 years now. I'll speculate that I made a minor bend in the rod. Works perfectly ever since.
     
  8. CanadaCat

    CanadaCat Well-Known Member

    You should have 2 holes marked standard and alt and a slot marked gauge. Bend the rod to slide it freely into the gauge slot while holding the choke closed with a cold engine, then put it in the standard hole, the alt is for operation in higher altitudes, I think over 2000’.
     
    techg8, BadBrad and Max Damage like this.
  9. BrianM

    BrianM Active Member

    This is what I needed to do and it worked. It is working better now but still needs another small adjustment but much better than it was. Thanks.
     

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