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van bogs down on normal acceleration

Discussion in 'Vans' started by roadmasterst, Oct 8, 2011.

  1. roadmasterst

    roadmasterst New Member

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    Looking for help./ 84 b250 with rebuilt 318 and 2bbl carter bbd mild cam(rv) single exhaust.
    reman carb reman distributor new plugs wires cap and rotor new 4pin control. fuel pump replaced ballast replaced,

    Engine runs fine on idle (20" vacuum) and at full throttle, however it bogs and stumbles on normal acceleration, worse when cold than hot. driving me crazy!!!!!!!!!!!!!!!!!!!
     
  2. ImperialCrown

    ImperialCrown Moderator
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    And if you let up slightly on the throttle, it resumes acceleration?
    It takes more voltage to fire a cold spark plug and a lean mixture than a warm one. Are these the correct Champions called for on the underhood label? Is the distributor advance running on ported and not manifold vacuum?
    The choke should also be operating and adjusted correctly for good cold driveability. The choke is fully open and out of the picture when the engine is warm. I have had my share of defective reman carburetors right out of the box. Do you still have a warranty on the carb?
     
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  3. skimask

    skimask New Member

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    20" vacuum at idle? Sounds bit high to me, like the idle is too high and it's already running on the mains rather than the idle jets, or possibly too much base timing. A thousand other variables come in to play with a tip-in stumble like this.
     
  4. roadmasterst

    roadmasterst New Member

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    Yes should be warranty on carb but symptom is identical to original carb that I replaced.
    Also running Autolite plugs and new delco wires.
    Going to replace choke stat and recheck vacuum break adjustment.

    What would the normal vacuum reading be on a stock engine such as mine. I thought that setting the timing to achieve max vacuum was a good way to go. After getting max vac I manually backed it off until no ping, and yes it is getting vac from the ported supply not manifold.
     
  5. ImperialCrown

    ImperialCrown Moderator
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    Actually you may want it to ping lightly when warm and accelerating briskly. If it has an EGR, you want that working as well.
    Autolite 66 cross over to Champion RN14YC. If you have an old Champion laying around I would compare tip reach and depth. I don't trust the cross-reference charts. They are more for marketing than finding an actual equivalent match. If the plugs have been in for time, do the tips indicate any lean mixture? Lean mixtures will tend to ping more. Does advancing the timing reduce the engine sag?
    Idle vacuum depends on a lot of variables. I would want to see between 17" and 20". A vacuum gauge is more of a diagnostic tool than a tool for setting timing or carb adjustments.
     
  6. roadmasterst

    roadmasterst New Member

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    Thanks Imperial Crown, running Autolite 65's and now that weather is colder and choke is functioning properly the engine runs great on choke however when choke off seems to run lean and bog down unless I give it full throttle.. I measured the voltage at the plus side of the coil and it reads 10volts is this normal voltage or is it low?

    Oh by the way picked up new choke stat and the replacement has an electric element as well as the bimetal spring, where is the best source to power it from?
     
  7. ImperialCrown

    ImperialCrown Moderator
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    Carb mid-range mixture sounds lean. I think that 1984 318's came with a Holley 2280. The truck didn't come with the Carter and we don't know the application of the carb that is on it. Is there a tag or carb # on the Carter?
    Coil voltage sounds about right while running. It drops through the ballast resistor and won't get the full 12 volts except when cranking.
    Choke heaters were usually powered though a 3-terminal oil pressure switch. The choke would start warming as soon as the oil pressure came up (engine running) and not before. You can add this or simply wire it to an 'ignition on' source (J2-Dk Blue wire).
     
  8. ccrider77

    ccrider77 New Member

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    Hopefully you got this figured out. Carb jet settings is a good place to start. Does the new carb have the same jet sizes as the original? If it runs better with the choke on, this could indicate a lean condition. Also you mentioned a remanufactured distributor. The vacuum advance on these (if it's equipped with vacuum advance instead of computer advance) must be set up with the correct advance curve. There were carb and distributor differences between California and 49-state vans. When you bought the rebuilt carb and distributor, it's critical to make sure they are correct for your van.
     
  9. roadmasterst

    roadmasterst New Member

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    I wound up installing a GM HEI dodge conversion distributor with a seperate power supply and now the firing up and running are great.
    Got rid of the resister issues and now seems bullet proof.
    Thanks for all the replies, and suggestions
    Great Web Site
     
  10. floridaman2013

    floridaman2013 Active Member

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    Wow, go figure! Lots of non-Mopar parts.
     
  11. valiant67

    valiant67 ...

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    The GM HEI conversion seems to be gaining in popularity. I think part of the reason is substandard quality on some of the control boxes Mopar sold in their conversion kits.
     
  12. floridaman2013

    floridaman2013 Active Member

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    Makes sense then. The only problems I remember about the HEI distributors when I was still working in the business was the ECU module inside would overheat and kill the engine. A lot of do it your selfers would not put the special insulating grease on the ECU before installing and caused the overheat condition on a lot of the modules.
     
  13. bguy

    bguy Well-Known Member

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    The position of the throttle blade at idle and just off idle is critical to vehicle drivability.
     

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