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400 small block trouble

Discussion in 'The Garage' started by .308fanatic, Feb 23, 2006.

  1. .308fanatic

    .308fanatic Registered Member

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    Still having some trouble with my chevy 400 small block. Runs rough when at an idle, good on the road. Sounds like it has a miss on the right hand bank. Can't seem to find it. It all started when the quadro-junk crapped out and started FLOODING one day while driving. Put in kit, adjusted best I could, now it seems to miss. Could it be from the cam?(owner said it had one, don't know the degree) Can anybody give me some pointers?
    Thanks.

    '79 GMC Jimmy 400sm, rest is stock.
    Don't look like much, but its got it where it counts.
     
  2. 1985_K5_Silverado

    1985_K5_Silverado 1/2 ton status

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  3. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    Done a tune up in ahile ( cap/rotor/plugs etc ) ?
     
  4. trailblazr81

    trailblazr81 1/2 ton status

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    Well.... What have ya done so far?? First thing I would look at would be plugs.

    Let us know what things youve already checked/fixed/replaced.
     
  5. .308fanatic

    .308fanatic Registered Member

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    Sounds kinda like that, just not as mean. Rough, hesitant idle on the right bank heard at the tailpipe.

    New plugs, cap, rotor, wires, coil, ect. Not the cheap s**t, work in a parts store, get it at cost.

    Smells like it is still a little rich too.

    Pretty new to v-8s, I'm an ex-dairyman, so I'm more used to diesels, tractors, and T**ts.

    Thanks for the help so far. Any other ideas? This place rocks. Gonna have to become a full member.

    Thanks again.
     
  6. trailblazr81

    trailblazr81 1/2 ton status

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    Well if your still rich, that could be causing problems at idle. Get the carb tuned right. Best way is with a vacuum gauge.
     
  7. .308fanatic

    .308fanatic Registered Member

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    I've never tried to tune a carb with vac. gauge before. Could you give me a few pointers on that.
    Thanks
     
  8. trailblazr81

    trailblazr81 1/2 ton status

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    Hook vacuum gauge to a port on the carb. Lean 'er out til yu get the most vacuum. Then your good to go. :waytogo: If she stumbles rich it up just a tad.
     
  9. .308fanatic

    .308fanatic Registered Member

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    Thanks man, I'll try it this weekend.
    Thank you all for the help, guys.
     
  10. mountainexplorer

    mountainexplorer 1/2 ton status

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    This probably isn't part of your problem, and it sounds like a different issue you're having. But if you happen to feel a constant vibration, check and make sure your flexplate has a balance weight on it for an externally balanced SB400. I've run into quite a few rigs that felt like they were running rough and vibrated at idle, and they were either 350's with 400 balance weighted flexplates, or 400's with internally balanced (no weights) flecxplates/flywheels. But this sort of "miss" or vibration is felt fairly consistently throughout the motor, and though more at idle... is also noticable at higher rpms.
     

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