66 Dart Gt slant 6 hesitation

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LuiG66

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OK, I've been working on this for a while the car idles great drives great but on first acceleration it hesitates to the point of wanting to (or does) stall.
I had the head redone (2 burnt valves) thought that was the problem. Changed the 1 barrel carb 3x, the timing is advanced as much as possible (by ear I think the harmonic balancer is tweeked out so timing light is out) what could be causing the hesitation? I heard someone mention that it could be the vacuum advance being stuck or bad or whatever. Any insight would be a great help since I'm on the verge of shoving dynamite down the carb
(frustrated after 2yrs of working on it). Thanks for all your help in advance.
 
You have changed 3 Carbs? Where did you buy them-- if they are from autozone/discountzone the remans are questionable.--- your off idle stumble is extreme if the car dies--- have you adjusted the valves-- & tuned up your ignition?
lots of info on slantsix.org-- on precise tuning for the slant--- Good luck, Lawrence
 
yeah all those things were done and 2 carbs were pro rebuilt I'm still thinking vacuum advance with more research.
 
vacuum advance is not going to stall your car--- disconnect it & see what happens-- sounds more like an accelerator pump problem.
also you timed it by ear/sight -- is not always very accurate-- you need to get at least a base line of where you are at--- your total timing might be off the charts.
 
LuiG66 said:
yeah all those things were done and 2 carbs were pro rebuilt I'm still thinking vacuum advance with more research.
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If your vacuum advance is stuck or not operating correctly the engine will stall... remove the vacuum line off the carb and plug it with something so you won't have a vacuum leak at the carb, drive it and see if it makes a difference.
If it drives the same I bet your vacuum advance is stuck or is leaking and needs to be changed out, The diaphragm in the vacuum advance has rotted and will not hold vacuum to activate the advance
some people pull the distributor cap off the distributor and suck on it to see if it is working by watching it as you pull vacuum on it manualy, When vacuum drops it should advance your trimming If it don't move and all you do is suck air the rubber has rotted, if you suck on it and it moves it's working.
I am not a tec, just a shade tree mec. Hope this helps :happy10:
 
thanks for that someone also mentioned the timing gear (nylon)? might have jumped? I'm trying to look at all the possibilities before I tear it apart & throw more money at it so any ideas are great .
 
Two things:
1 carb accelerator pump, even on a 'rebuilt' carb. could be bad.

2 Timing chain stretch from being old. Everyone thinks a jumped chain but that changes timing. You describe a bog or stall, so a jumped chain isnt correct.

thats all folks
 
Are you still running points? If so check the dwell. If the dist is worn the dwell will change enough that the spark becomes very weak. Also check the spark with the vac advance on and off. Should be hot in either position. Cap, rotor,coil or wires could be giving up also.
 
I'm going to throw my vote in with the "check the accelerator pump" crowd.

FWIW: I had a similar problem with the Holley 1945 on the 73 when I first got it. I determined the problem was the accelerator pump. Since I had never rebuilt a 1 bbl before, I got a Holley reman through Autozone. The carb had all of the correct connections for the installation. Bolted right up, the hesitation problem was a thing of the past. But it smoked like a factory until it got warm. Suspected jetting problem. The problem was the main jet was 12 sizes larger than what the FSM said should be in the carb. After re-building my factory reman, it works fine.

Sadly, rebuild kits that I found did not include parts to repair the accelerator pump. Also, it turned out I had to buy a complete kit just to get the fuel bowl gasket.
 
Play with the gas pedal a bit while idling (in P or N). Press it down (tap it a little) over and over quickly. How does the engine respond? Does the car have trouble idling immediately after?
 
MoparDart68 said:
Play with the gas pedal a bit while idling (in P or N). Press it down (tap it a little) over and over quickly. How does the engine respond? Does the car have trouble idling immediately after?
Click to expand...
I know this is an old thread but I’m having a similar issue and when I tried this test my engine started to stall.
 
Have you tried any diagnosis or are you simply throwing parts at it? Look into the carburetor throat and work the throttle (not running) and make sure there's a good strong stream of gas as soon as you open the throttle. The balancer is important. The timing is also important. If you're sure the balancer is slipped, replace it with a new one. If it's slipped, it's coming apart. Do you want the inertia ring and crank pulley slung into the radiator? What then? As it is now, you really don't know if the timing is advanced, retarded or where it is. I also agree with @memike. While on a V8, the vacuum advance doesn't affect running very much, on a slant 6 it can. You should verify that the vacuum advance is in good working order. If not, put a new one on it. Lastly, I assume this is a factory point type distributor. Get the dwell meter out and make sure the dwell is about 40 degrees. If the points are off and or worn, that can definitely cause a hesitation. Replace what you already know is bad, use a systematic approach and diagnose each system independently and you'll find the problem.
 
I’m not the OP. I’m experiencing hesitation off idle and I’ve been searching old threads. I was simply wondering what the significance was of the flowing test:

MoparDart68 said:
Play with the gas pedal a bit while idling (in P or N). Press it down (tap it a little) over and over quickly. How does the engine respond? Does the car have trouble idling immediately after?
Click to expand...
 
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