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Thread: Holley 4150 Quick Fuel Vacuum Problem

  1. #1

    Default Holley 4150 Quick Fuel Vacuum Problem

    Hi. Barnsydog, United Kingdom. I have a 502 BB Chevy that was fitted with a 871 Blower in a Glass 34 3 Window. Too quick for the street, so I removed the Blower setup. I fitted a Torker type Manifold (new) and a 780 cfm Quick Fuel Street/Strip Vacuum Secondary Spread-bore carb. The vacuum secondary won't open. I've changed diaphragm. I'm told the Silver spring may be too strong. Any ideas? It's running very rough idle slightly better when warm. The Cam is Isky lift .340" .358" can anyone help?

  2. #2
    Join Date
    Jan 2010
    Brisbane, Australia


    How do you know the secondaries aren't opening?
    Does it have the adjustable secondary opening rate screw?
    If the engine was built for a blower, the cam & compression ratio
    is probably not what you want for normally aspirated now.
    Your Quick Fuel carb is also a square bore, not a spread-bore.
    Regards, Gary

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