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Calling the Holley carb experts

Discussion in 'Engine & Performance' started by Dman1049, Jan 25, 2021.

  1. Dman1049

    Dman1049 Member

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    Sb400, Cam specs, duration @ 50, 224 224.
    Adv duration 298 298. Lift.465 .465 Lobe separation 107 117. 15inhg at idle. Holley 670 truck avenger. Have leaned the idle mixture out as much as possible at idle with the Engine still running. Plugs come out black. Sea level, low 30s to low 40s outside temp. How many jet sizes should I go down?
     
  2. Ricko1966

    Ricko1966 Full Access Member

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    I am assuming the choke is fully opening. That being said more than likely you have a blown power valve or the wrong power valve. You have 15 in at idle in drive? Than you should have a 75 power valve. Holley used to be maybe still are 1 or 2 backfires and the power valve is blown then that are super rich everywhere except WOT.
     
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  3. Dman1049

    Dman1049 Member

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    It's got a 6.5 in it. That test for the power valve is to screw the idle mixtures screw in while running. If it dies its not blown. It dies and havent had any backfires
     
  4. bucket

    bucket Super Moderator Staff Member

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    The newer ones don't blow valves like the old ones.

    How does it run? Is it doggy and sluggish? Does it cough and stumble? Have you tried different timing settings?

    The stock jetting should be decent for most average small blocks. Maybe not perfect, but close enough to run ok. Iirc, they come set up with a 65/69 maybe. Does the list # have a -1 or -2?
     
  5. Ricko1966

    Ricko1966 Full Access Member

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    I was assuming he is too rich at Idle which would mean an idle jet change if it doesn't have a blown power valve.Guess I should have asked the question have put a fresh set of plugs in it and done some WOT pulls on it to get a plug read?
     
  6. Dman1049

    Dman1049 Member

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    It loads up at idle... Blue smoke. Plugs have been changed 3 times. Twice they were wet and dripping. I assume the messed up choke cable was the culprit on that. Ngk xr4s are in now due to the camel hump heads. Was running ngk yr5s. They are black and sooty. I can get a list tomorrow. The carb is the newest version. Got it thanks giving directly from Holley. Stock getting is 68 main and 89 secondary. 6.5 power valve. Timing is 15 degrees adv and total of 36 degrees by 3k
     
  7. bucket

    bucket Super Moderator Staff Member

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    Checked the float level?
     
  8. bucket

    bucket Super Moderator Staff Member

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    I know it's new, but there could be some trash stuck in the front metering block.
     
  9. Dman1049

    Dman1049 Member

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    Had both bowls off. All clean. Also checked float level. Fuel level in the bowls is where it should be
     
  10. bucket

    bucket Super Moderator Staff Member

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    That jetting seems way off now that I went back through my notes. I don't recall what my old 670 TA came with exactly, but both my 670 SA's came with a 65/68 combo.
     
  11. Ricko1966

    Ricko1966 Full Access Member

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    Your main and secondaries have nothing to do with idle. Does the truck avenger have removable idle jets?
     
  12. Dman1049

    Dman1049 Member

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    It does have changeable jets
     
  13. Ricko1966

    Ricko1966 Full Access Member

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    Drop your idle jets 2 sizes at a time until you get where you can set curb idle with the mixture screw without it being all the way out or all the way in. There is no chance you have the throttle stop screw cranked in pulling fuel out of the transition ports at idle is there? Double check that.
     
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  14. Dman1049

    Dman1049 Member

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    I misunderstood your question. No idle jet to change. Only primary and secondary
     
  15. bucket

    bucket Super Moderator Staff Member

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    Are sure about that? It shouldn't.

    I'm leaning this way also, the transition slots may be uncovered. But why?


    Has the thing actually been driven, or does it run too poorly to drive it? I realize it runs rich at idle, but how does it run elsewhere and under load? How many turns out are the idle air screws? Have you looked down the throat of the carb while running, looking for an obvious defect like fuel dribbling out from anywhere it shouldn't be at idle?
     

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