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Thread: Holley carb 280Z

  1. #1
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    Default Holley carb 280Z

    I have a few questions for my 1978 280Z with a Holley 4160 (390cfm, pn 8007, arizona z intake). I'm new to carburetors in general, so I would really appreciate any help or at least pointing me in the right direction.

    1. Does timing stay the same? (10 degrees at idle)
    2. Does idle say the same? (800RPM)
    3. Is there a need to rejet? I believe mine has already been rejetted about 2 sizes down from stock, but I can't verify because I want to avoid opening it at this point.

    Right now the car actually runs all right. It starts fine with the electronic choke and the fast idle keeps it at 1500 or so. However, it idles around 1000 (and if I try to lower it, it starts to run rough between 800-1200). It is also harder to start when warm than when cold. There is a slight lag sometimes when pressing the pedal, but I can't tell if it is because the pumper is putting too much or too little in. I also can't reproduce it each time, so I'm not sure if that is the problem.

    Thank you!

  2. #2
    Registered User Kurbycar32's Avatar
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    That does sound like a timing issue. Older carb'ed Z's run timing at 17 degrees so try setting it there and see how it takes it, some people run in the low 30's so dont be afraid to set the timing by ear. Concentrate on getting the idle perfect: timing, cold and warm start and idle circuit on the carb. After that you can consider a rejet if you can't tune the rest of the carb correctly.
    Early 1974 260z
    https://sites.google.com/a/thecomputerrehab.com/260z/

  3. #3
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    wow, i wouldnt have guessed that. ill try it asap. thank you!

  4. #4
    Registered User porkbun's Avatar
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    The way I understand it (which could be completely wrong), total timing should be around 34 so initial timing depends on how much your vacuum and mechanical advance advance. Ive heard people with L28's run ~#54 jets which is 3 steps up from a stock 390cfm, my cammed l24 ran best with 55 jets. Checking your jets is as easy as pulling off the primary fuel bowl (which is only a hassle if you dont have the blue non stick gaskets). Idle should be the same and dont forget about the idle mixture screws when trying to change the idle. You can adjust when you want the choke to open and close by rotating the black electric choke cover clockwise or counterclockwise after loosening the three screws. The preferred pump cam among Z's is the orange pump cam. Kurbycars order of operations is correct
    Late 71' 240Z: HLS3040666

  5. #5
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    great info; thanks!

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