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Thread: Tuning ideas for 4776 DP on a 327.

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  1. #1

    Default Tuning ideas for 4776 DP on a 327.

    Here’s the car:
    '66 Nova
    .040” over 327, 10.3:1, Comp 280° hydraulic - 280° adv, 230° @ .050”, .480” lift, 110° LSA
    Dual-plane, Holley 4776 DP, Headers, 2.5” exhaust
    12 bolt, 3.73:1, 24.5” tire
    Muncie M21
    Street car only
    Idle vacuum @ 750 RPM is 9.5 inHg
    I would like a starting point for jetting & power valves. As well, carb part number is 0-80776 yet box says 600 CFM, mechanical secondary, square bore? Is this a 4776? Thanks in advance.

  2. #2
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    Similar to a 4776, but not the same.
    Have you tried the carb, since out of the box is pretty close straight up.
    You may find a 600 is a bit small for top end, but let's see how you go.
    4776-4 600 (F)66,(R)73 6.5 4150
    80776 600 (F)66,(R)73 6.5 4150 Mechanical
    Last edited by Gaz64; 03-04-2019 at 09:36 PM.
    Regards, Gary

  3. #3

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    Thanks for the quick reply. My research showed that the 0-80776 was a 4776 with a duel feed fuel line. Is it something more than the fuel line that makes them different?
    https://www.amazon.ca/Holley-0-80776.../dp/B004BS22C6
    As well, should I drop the power valve to a 4.5 or a 4 with my 9.5 in vacuum? Rob
    Last edited by H.O.rider; 03-04-2019 at 10:06 PM.

  4. #4
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    Hi Rob. Both carbs are 4150s with metering blocks on both sides, so they would accept the same fuel line assembly.

    Dual metering carbs 4150s take the same line, 4160s don't have a secondary metering block, so they take a shorter line.
    If you have 9.5 inches Hg in gear, then a 6.5 is fine. Fitting a 4.5 will create a fuel delivery "hole", where the engine might be under some light load at 6 inches, and no extra fuel from the PV circuit.
    You can experiment with this, but the "divide vacuum by 2 rule" is old school. The PV can be open at idle, and not make any difference to part throttle on the transition circuit. Gary
    Regards, Gary

  5. #5

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    I called the Holley tech line today to get the lowdown on the 0-80776. The young tech wasn’t quite sure what the part number was all about. He spoke with another more seasoned tech...LOL.
    The 0-80776 is a 4776 sold with a chrome feed line. The first tech said the list number would not change due to it being sold with a feed line. He came back and said, “I was wrong, that’s exactly what it is.”

  6. #6
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    What is the list number on the front of the choke tower? That's got to be a first for Holley to list a carb also as a different part number because they include a fuel line with it. Gary
    Regards, Gary

  7. #7

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    I guess those exhaust leaks fix on their own when the idle air screws are turned out a 1/2 turn.

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    So you have exhaust leaks that you know of at collector joints, etc.?
    Regards, Gary

  9. #9

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    Ended up with 69s in the primary. Car runs cooler and smoother. I can run the idle screws at 1 turn and get no popping. Transitions through fuel circuits seem great. Really liking the 600 double pumper.

  10. #10
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    69s are stock in a 4776, 66s in 4776-2 onward. So yours could be a leaner version (-2, -3 etc.) than earlier version of original 4776. A bit small for a 327, I ran a 4779 (750) on a 308. Gary
    Regards, Gary

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