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Low End Stumble?

Discussion in 'The Garage' started by Tweetysuarus, Jul 28, 2002.

  1. Tweetysuarus

    Tweetysuarus 1/2 ton status

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    Why is it when my rig is cold it really rips the rubber off the tires then when it warms completely, It stumbles on the bottom end,It has awsome Mid & Top end power. I have a new crate GM 350 H.O. w/ Edlebrock Performer#1400 Carb.w/elec. choke & Manifold. I'm considering changing the Distributor out for a Hi-Perf. Mallory or Accel /forums/images/icons/shocked.gif ? Not sure it would help my situation. /forums/images/icons/crazy.gif Any helpful suggestions would greatly be appreciated! /forums/images/icons/grin.gif
    Thanx,
    Bill C /forums/images/icons/confused.gif
     
  2. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Get a better carburetor and just tune the advance curve. All those ignition boxes is make you feel better in your mind. Your timing should be fully advanced by 3,000 RPM and be around 36 degrees with the vac advance disconnected. Use an adjustable vacuum advance can and add as much as you can until performance goes down.
     
  3. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    First off, what type of manifold are you running? is it a stock plane? or dual plane? a dual plane is designed for lower rpm torqe and also a #1400 is only a 600 cfm, wich should be ok, but you may need to go get a strip kit, and meter it most likely. last, what kind of advance are you getting on your hei? i have a sweet metered carb, and fattly curved setup for sale . pm me if interested...
     
  4. chulisohombre

    chulisohombre 1/2 ton status

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    mine runs the same way.when i first start it in the morning,it has at least 15 percent more power than when it warms up.i thought it was because of the choke being on so there is more fuel in the engine when its cold.but when i turn up the fuel screws to get more fuel,it still runs the same and i start to smell unburnt fuel coming out the exaust.im still trying to figure it out also.i got the same carb and edel intake also.i have hei with msd setup also so i dont think it is ignition problem.so when you figure it out maybe we can both have the problem solved /forums/images/icons/laugh.gif
     
  5. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Pardon my ignorance, but in the morning when the air is COLD, wouldn't the effect be that the engine is receiving a denser, colder charge of AIR?

    It sounds like when the engine running "leaner" is when it's more powerful, and as the air gets warmer the A/F ratio gets lower and runs richer....?

    That might also explain the low end sluggishness....too rich and loading up....?
     
  6. BurbinOR

    BurbinOR 3/4 ton status

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    Bill, your carb just needs fine tuned. Get a jet/metering rod kit and start having fun with it.
     
  7. Tweetysuarus

    Tweetysuarus 1/2 ton status

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    Gotta keep the one I got Ca. Smog has road side Inspections as well as normal station inpections! It SUCKS! /forums/images/icons/mad.gif
    Bill C /forums/images/icons/cool.gif
     
  8. chulisohombre

    chulisohombre 1/2 ton status

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    sorry about the way i worded it in my post.any time i first start it up when its been sitting and not warmed up.i seem to get more power out of it.would leaning out the mixture more be my fix.i guess i could try it and see,what do ya think?
     
  9. BorregoK5

    BorregoK5 1/2 ton status

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    I think everyone above hit a little piece of it. Start off by making sure everything is in good working order (tight bolts, no vacuum leaks, good thermostat, etc). Set your idle to around 850 rpm Verify your static, mechanical and vacuum advance timing to be correct. Hook a vacuum guage up to manifold vacuum and adjust your idle mixture screws in untill it stumbles and then out to where you get as much vacuum as your combination can produce, switching back and forth between the two until its even. Out too far and you'll loose vacuum again. Depending on your altitude and climate you may have to turn each in a half turn from this position.
     

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