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Thread: Air bleeds, jets fubar on this carb?

  1. #1

    Default Air bleeds, jets fubar on this carb?

    I have this old carb, probably customized in the '80s. It appears as the boosters have been changed out to a regular annular booster and the choke stack remove and blended a little.

    The back story time. I installed a wideband and went for a drive I was getting about 10.5:1 AFRs at cruise. I checked the idle vacuum and came up with 5 inHg.

    Changed the power valve down to a 2.5 and got not difference in the cruise AFR so I plugged the PV (at least for now) and went down to a 70 jet from a 74. In this state the AFRs cruise at 11.5:1 then drop to about 11:1 with more throttle. So I opened up the idle air bleeds about got it to cruise at about 13.5-13.8 from a .065 then +4 drill bits sizes. And getting into another 20-30% throttle (staying on the primaries) it drops to about 12.5:1 and as RPM increases leans out to 15.2:1 and I lift (4500 RPM or so maybe 5000).

    Everything I've been reading says that the annular booster should increase signal, yet my main jet air bleeds are .025" sized already, according to the Google. I should shrink my main air bleeds even smaller. Now I did.
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  2. #2
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    2,014

    Default

    Your idle jets are too big. Start there. Light throttle cruise is still too rich. Leaning off the main/PVCR is wrong path. Gary

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