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0-80555C vacuum ports, 4175 spread-bore replacement.

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  • 0-80555C vacuum ports, 4175 spread-bore replacement.

    Fitted the 4175 Spread-Bore QuadraJet replacement and wanted to connect my vacuum advance to a full manifold vacuum port instead of a ported vacuum source. Are any of the ports non-ported? The one shown for vacuum advance in the instructions appears to be ported, no vacuum at idle until throttle cracked. The one next to the front PCV port labeled as Purge has a slight vacuum around 5" at idle, but my engine produces around 18". Should any of the ports on the carburetor be pulling full vacuum at idle? Thanks.

  • #2
    The large PCV fitting has manifold vacuum, otherwise tee into the choke vacuum pulloff supply hose.
    The purge and the EGR nipples are "timed" ported, similar to the ported spark fitting on the primary metering block. All three of these pickup vacuum from different heights within the primary barrel. Gary
    Regards, Gary

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    • #3
      Gary, thank you for your prompt reply, very much appreciated. I'll try teeing into the choke pulloff hose. Don't suppose you happen to know the size of the tubing to the pulloff? I'm at work in the UK, but I'll try to pop into my local auto store on the way home this evening.

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      • #4
        I would say 3/16.
        Regards, Gary

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