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  1. #1

    Default Holley 5200 idle setting

    Since a few week-ends, i'm fighting with the carb of the Capri.
    Original carb was full of deposits and i wasn't able to clean it well, so i bought another, rebuilt, Holley 5200.

    The "new" carb is supposed to be a '76 Mustang one, except it doesn't have all the emission stuff of the '80 one and it's jeted way leaner (140p/132s instead of 179p/223s), it's the same carb, maybe with a bigger primary according to some internet sources (for me, looks exactly the same size).

    Problem i encounter is dealing with idle speed and mixture screw.
    My idle mixture screw doesn't seem to be of any effect when i try to lean it. I can close it fully and still have the engine idle, no effect on idle speed no matter which way i turn it. When i screw it counter-clockwise, vacuum goes up a bit and around 1t, starts to lower. Screw it clockwise 1/4t before it lowers but still idleing pig rich.
    Can lower the idle down to 1200rpm Neutral (21inHg), below, engine stumble (vacuum goes down to 15inHg, fluctuating up to 4-5inHg).

    Disassembled the carb today again. Transfer slot is not exposed on primary, secondary is slightly opened according to a rebuilt kit notice i have (adjusting screw seated + 1/4 turn). Checked float (brass) level, made it a bit low so not to flood the bowl.

    Car can run in this configuration, but mpg is close from the V8 ... not exactly what i need for a daily driver ...

    Choke is deactivated and all tune is done engine "hot".
    Vacuum advance is on manifold vacuum ... had heating problem previously when trying to run on ported vacuum ...

    Someone has an idea of what could be wrong ?
    '79 Pace Car 5.0 (well 4.2 until better days)
    '80 Capri 2.3 (sold ) - '79 Hatchback 2.3 (sold ) - '80 Notchback 3.3 (junk yard )

  2. #2
    FEP Senior Member dy85merc's Avatar
    Join Date
    May 2009
    parkersburg WV


    Whenever I had the problem with the air/idle not changing anything, it was usually a vacuum leak. Never know. Good luck.
    1985 mercury capri, 347, twisted wedge, TFS stage 3, Parker Funnel Web intake, demon 650, all MSD, 8.8, 4.10s, Hoosier QTPs...stock T-5 :0

  3. #3


    Tried spraying WD40 around hoses and base of the carb at lunch time. Didn't detect any leak.

    Maybe problem was related to EGR valve ... seems it's opened type. Just linked it to the EGR port of the carb, seems much better, idles lower with a relativly steady vacuum even if i can still close mixture screw without shutting the engine and the car stinks now but not rich as before (idle mixture set to 3/4) ... different odor i can't describe.
    '79 Pace Car 5.0 (well 4.2 until better days)
    '80 Capri 2.3 (sold ) - '79 Hatchback 2.3 (sold ) - '80 Notchback 3.3 (junk yard )

  4. #4


    Do you have the correct plate under it or do you have a huge vacuum leak at the back? When we put an 82 Mustang 2100 on our Jeep I noticed that there were 2 different bases to the carb and each had their own adapter. Base gaskets are also different

  5. #5


    I didn't switch from one model of carburetor to another, factory was a 5200 too so there's no need to change the base. Haven't detected any leak between EGR plate, spacer (new from rebuild kit) and carb though so problem doesn't seem to be there.

    Did some research and my mixture screw problem could also be related to the primary idle-jet ... maybe a bit too large (60 while usually seems to be 50 or 55) ... may try that as i have a 50 from original carb.
    '79 Pace Car 5.0 (well 4.2 until better days)
    '80 Capri 2.3 (sold ) - '79 Hatchback 2.3 (sold ) - '80 Notchback 3.3 (junk yard )

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