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Hot Rods 289 Bogging Down on Hard Acceleration

Discussion in 'The Hokey Ass Message Board' started by RednekYoga, Jun 11, 2019.

  1. RednekYoga
    Joined: Feb 2, 2019
    Posts: 21

    RednekYoga

    Hello HAMBones -
    My 63 Comet with a 66 289 2BBL fires right up and runs, but bogs down when I gun it. Especially off the line. I've got my timing set to 6 BTDC (that is if the balancer is where it's supposed to be). I have my dizzy vaccum advance running to the port on the passenger side of the carb, and the port just below the accelerator pump plugged up. Could I be using the wrong port for the dizzy?
    RNY
     
  2. rjones35
    Joined: May 12, 2008
    Posts: 851

    rjones35
    Member

    I'm sure somebody else will chime in....did this just start happening? How are the plugs, maybe it's too rich or lean? Fuel pump keeping up? Clogged filter air or fuel? I wouldn't think the distributor port would make THAT much difference, but you could move it and see what happens.
     
  3. 1-SHOT
    Joined: Sep 23, 2014
    Posts: 1,397

    1-SHOT
    ALLIANCE MEMBER

    Does the accelerator pump work ?
     
    Terrible80 likes this.
  4. flamedabone
    Joined: Aug 3, 2001
    Posts: 4,351

    flamedabone
    ALLIANCE MEMBER

    What is your total timing over 3K RPMs with the vacuum advance plugged? You also need to know what is happening with your fuel pressure at wide open throttle, but that is a little more difficult to figure out.

    Tell me your timing numbers first.

    -Abone.
     
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  5. You have a manifold vacuum advance dizzy and you are hooked up to the ported vacuum out let. Hook it to the one you have capped off under the carb.
     
  6. oj
    Joined: Jul 27, 2008
    Posts: 6,038

    oj
    ALLIANCE MEMBER

    Doubt it has anything to do with vacuum advance, thing is when you snap the throttle open you don't have any vacuum, the vacuum pot isn't that fast to respond but the timing is whatever the mechanical has given it.
    A bog is generally caused by having the throttle blades overly exposing the 'transfer slot' - what is that? The transfer is is that slot starting just at and extending above the throttle blade, you have to turn the carb over to see it. What it does is see's vacuum as the throttle blade sweeps past it and a small amount of fuel is drawn from it to give the engine extra fuel (this happens in milliseconds) to cover the engine until the fuel from the squirter is available.
    In short, you have your thorttleblades open too far at idle for some reason, the transfer slot is overly exposed and cannot see the vacuum when the throttle blades open for hard acceleration. If it were a 4bbl you could open the secondaries a little and then close the primaries. If you can't close down the throttle blades a common fix is to drill a .080 hole in each throttleblade, the Holley 4412 2bbl had them from the factory.
    Another very good possibility is if your car sat for a long time the alcohol in fuel has hardened the accelerator pump gasket, it'll make them hard as a rock. To test push down on the accelerator pump arm, if the gasket is good it will push down wih little resistance and a good flow of fuel will come out the squirter. If it isn't good it won't push down. Easy fix that. If an autolite it'll push 'in' not down.
     
  7. 6sally6
    Joined: Feb 16, 2014
    Posts: 450

    6sally6
    Member

    If you change the advance springs inside the distributor it will cure/greatly help with the bog...maybe.
    Several things COULD be causing it but timing is the place I would look. Bump it up to about 8*-10* BTDC and see if it improves. Bet it does!!
    IF you re-curve your distributor Google is your friend. I used this one to do mine.

    http://www.reincarnation-automotive.com/Duraspark_distributor_recurve_instructions_index.html
    Good luck......let us know what happens
    6sally6
     
  8. LM14
    Joined: Dec 18, 2009
    Posts: 1,429

    LM14
    Member
    from Iowa

    One thing to decide is if the bog is rich or lean. Here's my favorite way.

    Follow the car, have the driver romp it (you can romp it if you have a friend you trust more as a watcher than driver). If it bogs, blows out a cloud of black smoke then takes off, it's rich. If it bogs then gradually starts to catch up to itself, it's lean.

    Make sure the power valve is correct. Holley tech site has a very good description of how to do that.

    SPark
     
  9. deathrowdave
    Joined: May 27, 2014
    Posts: 1,439

    deathrowdave
    ALLIANCE MEMBER
    from NKy

    I cast my vote to looking into the vacuum advance unit and function . These play a huge role in how a Ford engine runs or doesn’t run properly . Way different advance mechanics happening than what happens in a GM distributer .
     
  10. saltflats
    Joined: Aug 14, 2007
    Posts: 9,125

    saltflats
    Member
    from Missouri

    What is the condition of the engine?
    Is it stock?
     
  11. sunbeam
    Joined: Oct 22, 2010
    Posts: 3,913

    sunbeam
    Member

    Does it come out of the bog or stay in it if the accelerator is held down?
     
  12. BoilermakerDave
    Joined: Mar 3, 2016
    Posts: 251

    BoilermakerDave
    Member
    from Las Vegas

     
  13. BoilermakerDave
    Joined: Mar 3, 2016
    Posts: 251

    BoilermakerDave
    Member
    from Las Vegas

    There is something to this. If you were to try straight manifold vacuum for your advance, you’d need to lower the idle at the carb, thus closing the throttle plates and fixing the problem described above.

    I’ve had good results with manifold vacuum - on most of my projects, anyway.
     
  14. David Chandler
    Joined: Jan 27, 2007
    Posts: 1,055

    David Chandler
    Member

    Does it do it when it's cold? With the choke only partially open, it would run richer. That could indicate fuel starvation down stream, being masked by the choke. How old is your fuel filter? How old is the timing chain? Could be lots of issues. But if it just started happening, my guess is the accelerator pump. On the plus side, that carb is about as easy as they come, as far as fixing them.
    Good luck!
     
  15. southcross2631
    Joined: Jan 20, 2013
    Posts: 2,571

    southcross2631
    Member

    Does it still have points ? Check for play in the distributor. Do you have a dwell meter ? If you hook it up and when you rev it up watch and see if the dwell changes .
    Do you have a hand held vacuum pump ? You can create your own vacuum source and check it out that way.
    Some other things to check while you are checking the accel. pump.
     
  16. RednekYoga
    Joined: Feb 2, 2019
    Posts: 21

    RednekYoga

    Fuel pump and carb are both new. Based on some below responses, I think it might be too lean in the idle. Is there a good guide for getting the idle adjust right? Thanks!
     
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  17. RednekYoga
    Joined: Feb 2, 2019
    Posts: 21

    RednekYoga

    Engine is stock as far as I can tell. The tag says 1966 289. The car was originally a 260 car.
     
  18. rjones35
    Joined: May 12, 2008
    Posts: 851

    rjones35
    Member

    Without being there it's kind of hard to say for sure, for me anyway. You might try the Holley website, they have some good tech on there somewhere. What carb is it anyway?
     
  19. Truck64
    Joined: Oct 18, 2015
    Posts: 2,965

    Truck64
    Member
    from Ioway

    "New" doesn't mean it's any good, especially these days.

    Use your vacuum gauge (nod your head "yes") to measure fuel pump pressure output at the carb inlet. Everything carburetor related, every setup, every adjustment, the calibration from the factory, is entirely dependent on the correct amount of fuel, not too much not too little delivered at all times under all conditions. If this is wrong it will never run right. Make sure the float height and fuel height is exactly on spec, lean out the idle mixture as far as it will consistent with a smooth idle.
     
  20. Terrible80
    Joined: Oct 1, 2010
    Posts: 652

    Terrible80
    ALLIANCE MEMBER

  21. RednekYoga
    Joined: Feb 2, 2019
    Posts: 21

    RednekYoga

    It's a knock of 2100 two barrel
     
    rjones35 likes this.
  22. RednekYoga
    Joined: Feb 2, 2019
    Posts: 21

    RednekYoga

    It comes out of it once it gets going. Then it's got good power.
     
  23. RmK57
    Joined: Dec 31, 2008
    Posts: 855

    RmK57
    Member

    Thats where I'd start.
     

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