1. Castle

    Castle Member

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    ill try to keep it short.... 1968 Newport...383 2bbl... I have a hesitation at slow speed, 25mph and under.... and also when I make a turn, at slow speed (as I turn, and start to accelerate, the motor stumbles) any ideas.... I have new gas tank, fuel sending unit, fuel lines to the carb, new fuel filter, and reman Carter carb. Thanks!
     
  2. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    Check the float level on your carb. If it is set too low, it will cause the engine to lean out.

    Dave
     
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  3. CBODY67

    CBODY67 Senior Member

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    What idle speed and mixture settings? Base timing? Sometimes, a hesitation can happen if the throttle plates are closed too much, which can alter the correct timing of when the transition port starts to handle the fuel supply transition between "base idle" and "run".

    Also, check to make sure the accel pump is working.

    At 25mph and under, with the stock 2.76 rear axle ratio, the trans should be at the bottom end of its speed range in "D"/3rd gear. Which would mean that a small amount of throttle to accelerate from 25mph and up would mean it was still in 3rd, with no automatic downshift into 2nd gear at that speed. As pre-'71 TFs did not part-throttle downshift for acceleration.

    As the car slows below 25mph, it probably should do an automatic downshift into 2nd gear, though, just as it will automatically downshift into low gear as the car nears being stopped.

    Youi might, for diagnostic purposes, see if it acts differently if you manually downshift into "2" below 25mph. To see if the accel response is better.

    Does this happen when the engine is cold or after driving about 10 miles or more?

    Just some thoughts,
    CBODY67
     
  4. rkrochen

    rkrochen Active Member

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    More info would be helpful but a quick answer would be to check the float and accelerator pump as mentioned.
     
  5. detmatt

    detmatt Old Man with a Hat FCBO Gold Member

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    If non of that works then check the length of your fuel pump pushrod.
     
  6. 67Monaco

    67Monaco Old Man with a Hat

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    After all that, check timing.
     
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  7. Ripinator

    Ripinator Senior Member

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    There you go again. . .
     
  8. detmatt

    detmatt Old Man with a Hat FCBO Gold Member

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    I can’t help it, it is very often applicable.
     
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  9. Castle

    Castle Member

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    Thanks guys, some good things to look at.
     
  10. Castle

    Castle Member

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    I tore the carb apart, today.... float is exactly to spec... accelerator pump and parts are functioning perfectly.

    I drove the car after warming it up, drove several miles, then went to town and drove the 30 mph in the village.... manually shifted into 2nd... made no difference... still hesitated.

    I find that if I accelerate gently, the engine stumbles until I get over 30 ish.

    If I punch the throttle from a stop, the engine does a big hesitation/ gulp, and then takes off like a rocket.

    I’m pretty confident my timing is where it should be

    I’m not confident on where my idle mixture screws are set.... I set them with a vacuum gauge, but I’m not getting a great feeling about it.
     
  11. detmatt

    detmatt Old Man with a Hat FCBO Gold Member

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    Your idle mixture screws don’t do anything unless you’re idling.
     
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  12. 67Monaco

    67Monaco Old Man with a Hat

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    Off idle stumble, bad accel pump or setting, timing, or vacuum leak.

    Spray some starter fluid around the vacuum hoses/lines and carb base. Note if the idle speed changes. If so you may have found your problem.

    It took me three carb rebuilds until I finally accepted my stumble was timing related not a fuel delivery issue.
     
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  13. rkrochen

    rkrochen Active Member

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    I agree you should check for vacuum leaks but wouldn’t recommend starter fluid. There are other products that work very well and aren’t so volatile. A good carb apart or carb out spray works just as well and is much safer.
    My money would be on the accelerator pump. Sometimes they look good but don’t work well. When this is occurring turn the engine off and while looking down the throat of the carb start opening the throttle. You should see the spray of fuel from the pump.
    However you can’t rule out other problems like timing or ignition issues.
     
  14. rkrochen

    rkrochen Active Member

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    Sorry should have said carb spray not carb apart.
     
  15. 67Monaco

    67Monaco Old Man with a Hat

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    OK whichever. I don't have to deal with OSHA so do what you have to do.
     
  16. rkrochen

    rkrochen Active Member

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    It not just that. Starter fluid vaporizes very easily and the vapours can easily get get sucked into the engine which will give you a false reading. Won’t happen with a product like carb out.
     
  17. 70bigblockdodge

    70bigblockdodge Old Man with a Hat FCBO Gold Member

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    Timing, timing, timing, and make sure mechanical advance is working /not stuck.
     
  18. Ripinator

    Ripinator Senior Member

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    Are you running a points ignition? If so, are the points in good shape, and are they properly gapped? If you aren't sure about them, install a new set of US-made NORS points and condenser and see if that helps. With my '66 300, I had hesitation issues that cleared up completely after I replaced these components. Halifax Shops @halifaxhops has everything you need for this.
     
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  19. Castle

    Castle Member

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    Ok, here is the current situation.... today, I opened up the distributor cap.... a pertronix unit, and switched out the springs inside the rotor.... the unit came from the manufacturer with their middle of the road tension springs installed.... I swapped out those ones for the softer springs.... two minute job.... started her up and started to roll out of my parking spot... before I made it 10 feet, I could already see a ton of improvement.... when I turned onto the highway, instantly pleased with a very smooth and non hesitating slow acceleration.... once up to 55 mph, cruised without any loping.

    So, I just needed the distributor to be able to advance easier, faster, completely... basically...

    Thank you for all the assistance, gentleman!
     
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  20. Ripinator

    Ripinator Senior Member

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    There ya go. The old adage is still true: Ninety-five percent of all carburetor problems are electrical. . .