My car has bog when secondaries open after swapping intakes at the track

Discussion in 'Street/strip 400/430/455' started by Tim, Sep 3, 2015.

  1. Tim

    Tim Silver Level contributor

    I have been leaving the line at about 3,000 rpms. I am shifting at 5,500 rpms. I did disconnect the the secondary choke pull off and blipped the throttle and the choke plates did open up easier, I then drove it. The bog was not as bad so I connected the pull off and blipped the throttle and the secondary flaps started to open. I drove it some more and it seems like the bog is
    much less than it was. I will try driving it again today and report my progress. Mark did email me the instructions on adjusting the spring tension which I will try as well.
    Tim
     
  2. LARRY70GS

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

    Driving it on the street will not be the same as on the track with sticky tires. The track may make the bog worse. I would try playing with the air door spring tension, and Cliff also makes a valve that goes in the vacuum line to the pull off. Between those 2 adjustments, you should be able to eliminate the bog.
     
  3. No Lift

    No Lift Platinum Level Contributor

    I just wanted to add a big "tip of the hat" to Tim. He's my kind of guy. Changing the intake at the track trying to get a real same day performance report. No BS "seat of the pants dyno" info. Hopefully everything will work out and he'll get the car into the 12's once everything is worked out.

    :TU:
     
  4. Tim

    Tim Silver Level contributor

    Mark sent me a link on how to adjust the secondary spring tension and I must say that after tinkering with it I finally got the bog to go away. Thank you Mark!!!!

    I sure wish I would have had this knowledge when I was at the track.

    Thank you to everyone for your suggestions and help.

    This web site is the best.

    Tim
     
  5. HotRodRivi

    HotRodRivi Tomahawks sighted overseas

    Now theres a happy ending , of the Buick kind. Not to be confused .........
     
  6. Gary Bohannon

    Gary Bohannon Well-Known Member

    I suggest opening the two little holes at the front of the air flaps to .055". Then cut notches into the flap edges with a die grinder to allow extra air flow. See Cliff Ruggles book for proper dimensions and locations. This made my qjet act like a Holley "double pumper", no kidding!
     
  7. Tim

    Tim Silver Level contributor

    Gary, thanks for the tip. Do you have a link to the book or do I need to buy it?
    Tim
     
  8. Bigpig455

    Bigpig455 Fastest of the slow....

    Buy it - it's a really great book. I do this to all my Q-Jets, and I've never had any kind of bog issues.
     
  9. BuickGSrules

    BuickGSrules Gold Level Contributor

    You can buy it at cliffshighperformance.com
     
  10. LARRY70GS

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

  11. Tim

    Tim Silver Level contributor

    Just an FYI, John Osborn rebuilt my carb years ago for my engine specs and it has ran flawlessly until I switched intakes, maybe John had already made these changes.
    Tim
     
  12. Tim

    Tim Silver Level contributor

    My hesitation never went completely away, it really is not a bog, it’s more of a hesitation.
    I swapped the intakes back and I still have the hesitation at wide open throttle from a start and on every shift if I floor it.
    The hesitation is very slight if I just slowly roll into the throttle.
    Any help would be appreciated.
    Thanks
     
  13. matt68gs400

    matt68gs400 Well-Known Member

    I’m still in awe that you swapped an I take at the track. Lol. Looking to do an intake swap next week! Inspiration!
     
  14. LARRY70GS

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

    You need to take advantage of JW's offer and have him weld a bung into your exhaust.
     
  15. Tim

    Tim Silver Level contributor

    I wish I could Larry, unfortunately I moved about 200 miles from Jim so not so easy to get to him.
    Tim
     
  16. TORQUED455

    TORQUED455 Well-Known Member

    What carb number are you using? You really need the primary choke pull-off hooked up and working. If you disconnect the vacuum hose to it (engine off), push in on the lever, put your finger over the vacuum nipple, what happens when you let go of the lever? If the pull-off is leaking a bit, it will still hold the secondary air valves closed at idle, but will bleed off vacuum too fast causing the valves to open too quickly, resulting in a bog or hesitation.

    If the choke pull-off is good, try tightening the secondary air valve wind-up (3/32” Allen screw and small flat screwdriver) 1/8 of a turn; rinse and repeat until you tune the hesitation out. This of course assumes that the hesitation is caused by the secondary air valves opening too quickly.

    What is your ignition set-up? Plug brand, heat range, cap, rotor and wire brand, trigger source and have you checked to make sure your total timing is “in” very quickly? Are you using a vacuum advance?

    I have used Qjets on both SP1’s and SPX’s with no hesitations whatsoever, albeit with automatic transmissions. I’m sure the extra load during the shifts on a 4-speed isn’t helping things out much.
     
  17. Tim

    Tim Silver Level contributor

    I will try your suggestions however this carb worked flawlessly for 6 years until I switched intakes it started to hesitate, I thought it was due to the SP1 intake so I changed back to my Edelbrock and the hesitation is still there .
    Thanks
    Tim
     

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