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

Dsertdog

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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
 

Turboomni

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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.
 
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CBODY67

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G'Day,
Ain't no Expert but back in the 70s I had a383 2 bbl that had a really annoying habit of "Nudgeing". When you were cruising on Trailing Throttle the car would "Nudge Nudge" as though it was sort of missing but not really, it was REALLY Annoying. Your Foot wasn't really "On" the throttle but neither was it off. Long Story short one of my Club members told me the air filter Bolt on a Carter 2bbl Carby doesn't go all the way into the body of the Carburettor and if you have a habit of over tightening the Wingnut it ends up pulling the top plate away from the Body of the Carby allowing fuel to splash over into throat. I removed the top and used a sheet of Glass & sandpaper and sure enough you could see where the Top had pulled away from the Gasket. A bit of work gently Tapping & Sanding it level, a New Gasket & that cured my Problem. Might be worth checking. Hope this Helps.
Kind Regards, Tony.M (Oh & Tighten Gently in the Future)

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
 

NWPT70

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

If you put a new electronic dist in it most likely has too much vacuum advance at cruise rpm. Use a 3/32nd Allen wrench right though the nipple and tighten it up test, tighten it up test, tighten, test until you get rid of the surge. Could be lean as mentioned, but with exhaust manifolds I'm guessing not.
 

70bigblockdodge

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

CBODY67

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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
 

Turboomni

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

70bigblockdodge

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

NWPT70

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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.
 

Turboomni

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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.
 
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NWPT70

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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!
 

NWPT70

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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.
 

Turboomni

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

NWPT70

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Are you sure your vacuum advance is connected to the correct vacuum port? You have manifold vacuum and ported vacuum.
The vacuum advance is hooked up to the ported vacuum supply line on the carburetor. I have the 2 barrel Carter BBD.
 

NWPT70

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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
 

70bigblockdodge

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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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