Page 1 of 2 12 LastLast
Results 1 to 10 of 16

Thread: Tuning ideas for 4776 DP on a 327.

  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
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    1,534

    Default

    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

    Default

    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
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    1,534

    Default

    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

    Default

    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
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    1,534

    Default

    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

    Default

    0-80776 is stamped on the choke tower. Tech came back after talking to another tech and he said the same...LOL.

    It’s exactly as this Amazon ad describes: https://www.amazon.ca/Holley-0-80776.../dp/B004BS22C6

  8. #8
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    1,534

    Default

    That explains how the Holley list numbers became so big. Just makes it more confusing. Gary
    Regards, Gary

  9. #9

    Default

    I installed the 4776 DP and used the same initial jetting specs as the 1850-2 Vacuum carb. Things are working well and I'm experiencing something on both carbs that I’d like some opinions on. When I set the idle screws to maximum vacuum at idle, which is roughly 1 to 1.25 turns on both carbs, I get a pop through the exhaust when shifting at 3000ish RPM from 1st to 2nd. If I enrich the idle screws to 2 turns, this goes away. Is this a sign that my primary main jet is too lean?

  10. #10
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    1,534

    Default

    The camshaft wants more idle circuit fuel. The part throttle is a tad lean on the idle/transition circuit, and hence the ignition in the exhaust system. If you drill the IFRs out in .001 steps, you'll find the mixture screws will end up at 3/4 to 1 out. You need a pin gauge set to size them first. You really need a carb with four corner idle adjustability once you have any camshaft wilder than about 225° @ .050. Gary
    Regards, Gary

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
About us
Holley has been the undisputed leader in fuel systems for over 100 years. Holley carburetors have powered every NASCAR® Sprint® Cup team and nearly every NHRA® Pro–Stock champion for four decades. Now, Holley EFI is dominating the performance world as well as our products for GM's LS engine. Holley's products also include performance fuel pumps, intake manifolds & engine dress–up products for street performance, race and marine applications. As a single solution, or partnered with products from other Holley companies - Hooker Headers, Flowtech Headers, NOS Nitrous, Weiand, Earl's Performance Plumbing, or Diablosport - Holley products can give you the edge you need over the competition.
Join us