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Projects 283 Fuel Delivery and MPG

Discussion in 'The Hokey Ass Message Board' started by BowtieGoofy, May 8, 2019.

  1. BowtieGoofy
    Joined: Feb 13, 2019
    Posts: 74

    BowtieGoofy

    I have a 283 bored 60 over with a stock type cam and 601 casting heads that currently has an Edelbrock Tarantula single plane manifold with a Q-Jet on it. I’m not changing my carb, so please no Q-Jet bashing.

    I know the manifold is not optimal, but it was free so I could get the motor running. We built everything and set the carb in the cooler air in Prescott, AZ. I live in the Phoenix area, where it’s much warmer. I find that I am having issues where the motor bogs from idle when I hit the accelerator. I know Q-Jets have a reputation for this, but when we set it up at the higher altitude in cooler weather, we never had this problem.

    I read that single plane manifolds can contribute to this because at low RPMs there is not enough turbulence in the chamber to sufficiently deliver the fuel to the heads. I also believe my carb needs to be adjusted.

    I also wanted to know if the single plane manifold is having an adverse affect on my gas mileage compared to a Dual plane. I can get a cast iron dual plane for $25 locally or a Weiand Action Plus aluminum for $100.

    What advice might you more experienced hot rodders have for me?
     
  2. Truck64
    Joined: Oct 18, 2015
    Posts: 5,325

    Truck64
    Member
    from Ioway

    Looks like there's a 4,000 ft elevation change, carb might need some adjustment. Wouldn't hurt anyway, it will run leaner in your case.
     
  3. squirrel
    Joined: Sep 23, 2004
    Posts: 55,935

    squirrel
    Member

    I've done well with the stock iron Q jet type intakes under Q jet carbs. I would try that first. cheap, might help.

    I have not bothered with resetting the jetting on the Qjets, I live in AZ at 4500 feet, and drive to the lower elevations. They worked fine on the original applications with those elevation changes, you know.

    What cam is in the engine? and how is the car geared? that might have some influence
     
    Truck64 likes this.
  4. Stock cam, stock head specs similar to 520 pp.. Surprised it runs even halfway decent with that manifold. It's going to be hard to set the carb up with that combo. MPG? Forget about it. What did the carb come off of? What primary jets are in it now?
    There were some late 70's aluminum manifolds on 305's and 350's. They would probably match the heads better than an early pre- EGR 327 /350 manifold..Not sure about 601's though. No experience with them as far as matching up ports.
     

  5. sdluck
    Joined: Sep 19, 2006
    Posts: 3,186

    sdluck
    Member

    this is a common problem on q jet,good carb. Have you done the accelerator pump mod?
     
  6. Better tell him which one. There's about 4 or 5 ..Probably more;)
     
  7. sdluck
    Joined: Sep 19, 2006
    Posts: 3,186

    sdluck
    Member

    Cut 1/8 inch off top of the accelerator pump Rises up further and has a longer squirt

    Sent from my SM-J737T using The H.A.M.B. mobile app
     
  8. That's one. You can also add a third hole in the arm and re-bend the link for more travel...
    But wait ..He could be describing the ol' Quadra -bog thing from the secondaries.
     
    Last edited: May 9, 2019
  9. carbking
    Joined: Dec 20, 2008
    Posts: 3,715

    carbking
    Member

    Without knowing more about the carburetor (Rochester AND Carter made hundreds of different Q-Jets), really impossible to arrive at a precise conclusion.

    Often, hesitation from a stop sign is a direct result of setting the idle too fat (which might be required with your combination).

    Not saying it will help but it might: turn the idle mixture screws in until the engine almost dies, and readjust your idle with the throttle positioner screw.

    And the Q-Jet, well the 1968 and newer anyway, was and is an excellent carburetor. The 1965~1967 versions need a carburetor guru to breathe on them.

    As far as the stuff you get/got for free: check out the second line in my signature block ;)

    Jon.
     
    XXL__ and belair like this.
  10. BowtieGoofy
    Joined: Feb 13, 2019
    Posts: 74

    BowtieGoofy

    From what I understand, my carb is off a ‘73 C10. It was totally rebuilt by a friend of my dads who went to the Rochester school back on the day. These are his specialty. I don’t think it’s related to the secondaries because I’ve only had those open about 5 times total. I take off slow.

    I’m looking for a new manifold because I believe this is a huge part of my issue. I’ll also try resetting the idle mix as suggested after I get that changed.
     

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  11. BowtieGoofy
    Joined: Feb 13, 2019
    Posts: 74

    BowtieGoofy

    Car has a very mild, stock type cam and is geared with 3.55s I believe. Nothing crazy at all.
     
  12. 4 pedals
    Joined: Oct 8, 2009
    Posts: 958

    4 pedals
    Member
    from Nor Cal

    Getting a dual plane under it will make a difference for the better. Another question, what trans is behind it?
     
  13. BowtieGoofy
    Joined: Feb 13, 2019
    Posts: 74

    BowtieGoofy

    TH350 trans. I moved to that from a Powerglide originally. Want to go to a 700r4 eventually.
     
  14. BowtieGoofy
    Joined: Feb 13, 2019
    Posts: 74

    BowtieGoofy

    It could be 3.36s or 3.55s. Not sure from the research I’ve done but it is one of those 2.
     
  15. BowtieGoofy
    Joined: Feb 13, 2019
    Posts: 74

    BowtieGoofy

    I replaced the Tarantula with a Performer and re adjusted the carb. I don’t get the bog off the line I used to get. I need to set the timing again as I do have a very small stumble in the idle, but overall things are so much better. I did not lose any acceleration performance at freeway RPM at all, and around town driving is so much more fun.
     
    Truckdoctor Andy and Dyce like this.

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