Anyone else have minor hesitation/jerking at part throttle??

Engine, Transmission & Driveline

  1. Dsertdog

    Dsertdog Old man with an old guitar, and a blue note. FCBO Gold Member

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    I had all kinds of surging issues that were caused by a combination of leaking booster and stuck advance springs.
    As mentioned, dual exhausts tend to lean up the fuel mixture. Try bumping your initial back two to four degrees, reset your idle, and see what happens
     
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  2. Turboomni

    Turboomni Old Man with a Hat

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    I remember a similar situation on my Fury. Cruising at light throttle it would not be steady especially going up a slight hill. Engine speed would slightly vary. My vacuum advance canister had a slight to moderate leak. My guess is the leak wasn't stable and would advance and retard advance in a random way slightly.
     
    Last edited: Aug 23, 2020
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  3. CBODY67

    CBODY67 Old Man with a Hat

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    On the Chrysler OEM Stromberg WWC 2bbl of the middle 1960s and the Holley 2210/2245 2bbl that was used from 1971 and later, the air cleaner stud issue WAS prevalent. But the Carter BBD 2bbl uses a heavy wire which snaps into each side of the throttle body to hold the air cleaner stud itself, so the over-torque of the air cleaner wing nut puts that force around the edges of the throttle body rather than into the center of it . . . where the seals for the rear of the carb fuel bowl is AND where the vac passage that goes to the power valve (on the WWC and the Holley) is located and sealed with the air horn gasket.

    On the Stromberg, the issue was noticed back in the later 1960s after a carb rebuild. The old-line Chrysler service manager mentioned using a piece of glass and some sand paper to "surface" the warp out of the upper carb body. I used two air horn gaskets with a bit of silicone sealer in the center. Which worked as long as the silicone didn't deteriorate with its exposure to gasoline. I could tell when it needed replacing as when the choke plate was partially closed, it would pull fuel from the float bowl into the venturi area, resulting in a very rich warm-up mixture.

    FWIW, that similar over-torque of the air cleaner wing nut issue could be an issue with any carb that puts the air cleaner stud directly into the carb air horn. Apparently, the air horn castings in other carbs are strong enough to prevent it from upward-warping their air horns?

    Enjoy!
    CBODY67
     
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  4. kingbowl93

    kingbowl93 Active Member

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    I will give this method a shot. How much of a turn increment do you recommend each time?

     
  5. 70bigblockdodge

    70bigblockdodge Old Man with a Hat FCBO Gold Member

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    If it is really loose which most replacements are it seems. Probably a couple- three to start, then 1/2 turn if still misbehaving. That should ballpark you.
     
  6. CBODY67

    CBODY67 Old Man with a Hat

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    If you have a hand-held vacuum pump, you can find some FSM specs on the vacuum advance, when it starts, and adjust the spring until the arm just moves at that vac level. The FSM's distributor specs will detail the start and max advance vacuum levels. Don't worry about the degrees of advance provided, just when it starts. See how that goes.

    Just some thoughts,
    CBODY67
     
  7. Turboomni

    Turboomni Old Man with a Hat

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    See if your vacuum advance holds vacuum first! If not replace and go from there.
     
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  8. 70bigblockdodge

    70bigblockdodge Old Man with a Hat FCBO Gold Member

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    See there you go with proper setup and procedures.:poke:
     
  9. kingbowl93

    kingbowl93 Active Member

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    So the vacuum canister holds vacuum and I was only able to turn in the hex screw 180° before hitting the bottom. I will be taking a test drive to see if that half turn helped. A bit concerned since I have no more room for more clockwise adjustment. Will try adjusting the base timing next 2+/- as previously suggested.
     
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  10. Turboomni

    Turboomni Old Man with a Hat

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    Turning the hex screw adjustment and bottoming out in the clockwise direction allows the most vacuum advance and the spring will apply the least tension on the diaphragm. Turning counter clockwise will apply more pressure to the spring and load the diaphragm then restricting its movement and less vacuum advance timing. You by bottoming out the the adjustment clockwise have loosened the tension on the diaphragm and increased the amount advance travel. The diaphragm will be the most un dampened adjustment. Counter clockwise will stiffen the diaphragm with spring pressure and restrict diaphragm movement and the amount of vacuum advance applied. If this is your problem I believe you went the wrong direction as the diaphragm is now as loose as it can get. I would try counter clockwise and dampen that diaphragm. I took one apart a few years ago to see .
    The adjustment here would be the least vacuum advance and most damping of the diaphragm.
    20200825_115425.jpg This is your position now at full clockwise adjustment.
    20200825_115451.jpg Pic of adjustment screw all housed inside the canister.
    20200825_115435.jpg

    You could try removing and capping off the vac line to see if it is in fact your problem too as a test.
     
    Last edited: Aug 25, 2020
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  11. kingbowl93

    kingbowl93 Active Member

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    Thanks for the tip @Turboomni . I was following the advice from someone else who posted the recommendation above to turn clockwise. I will try counterclockwise!
     
  12. kingbowl93

    kingbowl93 Active Member

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    I will try capping the vacuum line also. By the way I should mention I am still learning what vacuum advance is even for. I am a novice still in understanding the whole principle of it.
     
  13. 3175375

    3175375 Senior Member FCBO Gold Member

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    Ignition timing - Wikipedia
     
  14. Turboomni

    Turboomni Old Man with a Hat

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    Are you sure your vacuum advance is connected to the correct vacuum port? You have manifold vacuum and ported vacuum.
     
  15. kingbowl93

    kingbowl93 Active Member

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    The vacuum advance is hooked up to the ported vacuum supply line on the carburetor. I have the 2 barrel Carter BBD.
     
  16. Turboomni

    Turboomni Old Man with a Hat

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    :thumbsup:
     
  17. kingbowl93

    kingbowl93 Active Member

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    So just an update- capping the vacuum advance line at the carb causes the car to have an off idle bog and a pretty decent part throttle surge that wasnt there before. What do you think of this? @Turboomni
     
  18. 70bigblockdodge

    70bigblockdodge Old Man with a Hat FCBO Gold Member

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    You need more initial timing.
     
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  19. kingbowl93

    kingbowl93 Active Member

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    That is going to be my next move. For starters , what is the initial timing these cars supposed to be set at ?
     
  20. 70bigblockdodge

    70bigblockdodge Old Man with a Hat FCBO Gold Member

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    My general rule of thumb is 12-14° initial. Add the 20-23° average of mechanical, that puts you at a max of 37° (14+23) total timing at WOT. As long as it is not pinging/detonating it is good.
    What it is supposed to be set at is probably in the neighborhood of 6°, guessing.
     
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