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help me tune this thing!

Discussion in 'The Garage' started by Jonny-K5, Oct 10, 2004.

  1. Jonny-K5

    Jonny-K5 1/2 ton status

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    heres the stats: 1970 350 chevy, newly rebuilt. HEI ignition
    edelbrock 750 manual choke carb.

    problem: it runs great when cold. but after its been at running temps for 5-10 mins it seems to be either running rich or missing. what happens is if i blip the throttle (idle to 2000rpm) black smoke comes out of the pipes and sounds rougher than when cold. it runs great when driving it,only problem is in neutral and blipping the throttle.

    i've replaced plugs,wires,cap&rotor,coil, tried everything from leaning out the carb 10% to richening it 10%.installed smaller accelerator pump nozzles. i cant seem to figure this one out.choke is manual and wired solid,so i know it not a factor.

    im thinking maybe the ign. module may need to be replaced, maybe my plug wires are arcing over, or something else related to heat soak.

    how should the wires be routed? ive heard that they are supposed to overlap each other to prevent crossfiring. ive also heard this causing crossfiring. what is correct?
     
  2. Jonny-K5

    Jonny-K5 1/2 ton status

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    ttt,anyone?
     
  3. hawkeye649

    hawkeye649 1/2 ton status

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    How strong does your spark look?

    I had an S10 that died out in a smokey mannor when my charging system went caput.
     
  4. Jonny-K5

    Jonny-K5 1/2 ton status

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    i havent checked the spark lately. i know it shocks the hell outta me when messing w/ the dist.
    i'll check that tonight, thanks
     
  5. semper-k-five

    semper-k-five 1/2 ton status

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    do you have ur vac advance connected on the left front vac port on the carb?? i had a similar prob and that was the cause....if it were running rich enough to effect ur idle, i would expect some back firing through the exhaust...

    did you use a vac gauge to tune???
     
  6. Jonny-K5

    Jonny-K5 1/2 ton status

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    checked timing again w/ vac gauge, checked spark as well, all good. advance is hooked up to the right port. i think its just more tuning needed in the carb. i'll probly take it to a carb shop and let them tune it and see what they say, thanks guys
     
  7. dontoe

    dontoe 3/4 ton status GMOTM Winner

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    Pretty much the exact same thing I experienced when I put an HEI distributer in my 74. I used the original wire and it ran great until it warmed up. I replaced the wire with a larger gauge from the fuse panel and it's ran perfect since.
     
  8. m j

    m j 1/2 ton status

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    sounds fat
    lean it
     
  9. Jonny-K5

    Jonny-K5 1/2 ton status

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    [ QUOTE ]
    Pretty much the exact same thing I experienced when I put an HEI distributer in my 74. I used the original wire and it ran great until it warmed up. I replaced the wire with a larger gauge from the fuse panel and it's ran perfect since.

    [/ QUOTE ]

    really? hmmm, thats worth a shot. /forums/images/graemlins/thumb.gif

    [ QUOTE ]
    sounds fat
    lean it

    [/ QUOTE ]

    i dont think its too rich, i've leaned it out as much as they suggest in the tuning chart. didnt help, just lost power.
     

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