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Thread: Noticed loose clutch bolts on the rear metering block on a 4160 marine carb.

  1. #1

    Default Noticed loose clutch bolts on the rear metering block on a 4160 marine carb.

    Got a question about the 4160 marine carb I tried to use on my 1988 OMC/Chevrolet 4.3. This carb was sold by Holley as specifically set up for Chevrolet 4.3 V6. It never ran right, running extremely rich, turned 2 sets of plugs black and I wound up wasting months to try to get this thing to work (brand new carb, but out of warranty). In disgust I pulled my old QuadraJet off the shelf rebuilt it and it was fine, 100% better than the Holley. I was still curious so I took the Holley completely apart a few months later. Check the floats, needle valves, etc., when I was trying to get it to work, made sure the air bleeds were not plugged, transfer slot not over exposed, etc. Then when I took off the rear bowl, I noticed the clutch bolts for the rear metering plate were loose, barely hand tight. Question, since the Holley runs off both the primary and secondary float bowls all the time, could this have caused the chronic rich running issues? I would have liked to be able to use a new carb to have less maintenance issues but this sure didn't work out that way!

  2. #2
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
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    1,941

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    Yes.
    The secondary non-adjustable constant feed idle circuit is fed by an IFR, (idle feed restriction) within the secondary metering plate.
    The secondary bowl contributes to overall fuel flow into the engine to allow fresh fuel into the bowl, and so minimize fuel "going off" in the secondary bowl, from lack of secondary use, such as continuous light load driving.
    With a loose plate, fuel could then flow along an additional path in parallel with the IFR and the engine would be rich, possibly to the point of impossible to adjust for a clean idle. Gary
    Last edited by Gaz64; 07-06-2020 at 10:03 PM.
    Regards, Gary

  3. #3

    Default

    Thank you Gary for helping me solve the mystery. Now if anything happens to the QuadraJet for which there are no more good cores left, I can use that still brand new Holley sitting in the box on the shelf that the QuadraJet used to be sitting on!

  4. #4
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
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    1,941

    Default

    Glad to help Lou. Gary
    Regards, Gary

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