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Carb tuning 101

Discussion in 'The Garage' started by 78Suburban, Apr 4, 2006.

  1. 78Suburban

    78Suburban 1/2 ton status

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    I'm wanting to fine tune the Idle mix screws on my ebrock performer. I know I can back each one out till I see a small increase in RPMs, but I don't have a good tach that I can simply plug into the motor. Can I just use a vaccume guage and turn each screw untill I get the highest vaccume reading? What is a good vaccume number to look for?
    thanks,
    James
     
  2. jaredmajor

    jaredmajor Registered Member

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    Yeah the vacuum gage is the other way to do it. Or by ear with the rpms. I have a tach, but i do it by ear. Vacuum readings, you just want the highest vacuum reading, this will all be dependant on what cam you are running, bigger cam lower vacuum at idle.
     
  3. 78Suburban

    78Suburban 1/2 ton status

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    is using vaccume a fairly precise way to do it? Should I turn them all the way in, then 2 1/2 turns out and start tuning from scratch, or should I simply try turning each screw in and then out and see what raises the vaccume? I know I need to do one at a time.
    thanks,
    James
     
  4. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    I use a vaccum gauge and it is dead on balls accurate. I recomend turning both screws 1/8th at a time. The goal is to achieve the highest vaccum.
     
  5. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    Definitely no more than 1/8th of a turn. One time a mechanic showed me on their fancy tailpipe machine the difference a minor turn on the mixture screw can make. I was surprised.
     
  6. Triaged

    Triaged 1/2 ton status

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  7. norville

    norville 1/2 ton status

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    I'm pretty sure E-brock has a procedure for doing it. I thought it was 1 1/2 turns out and go from there.

    bob
     
  8. littlejimmythatcould

    littlejimmythatcould 1/2 ton status

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    I agree with the 1 1/2 turns before you start tuning. A metering rod kit would help fine tune it even more. Also adjusting your accelerator pump to your personal needs could help too.
     

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