Fuel/air mixture ratio??

Small Block Mopar Engine

  1. JAY SINN

    JAY SINN GT67DART

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    My dart will run. But when I push down too hard on the gas it hesitates and if I don't let off the gas it dies. What do I do? It's a 340 Plymouth roadrunner motor. 71.
     

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  2. Woods74

    Woods74 Broke Senior

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    You didn't get a wide-band o2 sensor. Innovate LC-2 FTMFW.
     
  3. 72bluNblu

    72bluNblu FABO Gold Member FABO Gold Member

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    What carburetor? What kind of build on the engine? What ignition system? Any recent changes to the carb or distributor? Is the carb new? Rebuilt? Same for the distributor and engine itself.

    You could be running really rich, but you could also have the wrong timing advance or other ignition problem. We need more information.

    While a wideband A/F gauge is nice to have, people have been tuning engines for a long time without them. Even if you have one, it only tells you if/when you're rich or lean, not what's causing it.
     
  4. crackedback

    crackedback FABO Gold Member FABO Gold Member

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    Ignition timing should be your first stop.

    Throw the book numbers out the window if you don't need to pass emissions. I time stock 340's in the 14-18 range at idle. Set it there and see if it helps with your hesitation. DO NOT hammer on it with this changed, you can hurt the engine because total will be too high. Fix mechanical advance to hit your total number.

    If you have the T-quad on it, that may be another area issue.
     
  5. trapster

    trapster Well-Known Member

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    check your vacuum advance
     
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