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injectors for a 392

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  • injectors for a 392

    Ok, so I've seen that you can get different injectors for the 350 and also the 454, but which ones would be closest to stock cfm's ect... for a 392? Also what injector size would you recomend for a slightly moded 392 as in, heads that have been gone through, port matched, smoothed, ect..

    Thanks
    Mark

  • #2
    Re: injectors for a 392

    Originally posted by moosebrew
    Ok, so I've seen that you can get different injectors for the 350 and also the 454, but which ones would be closest to stock cfm's ect... for a 392? Also what injector size would you recomend for a slightly moded 392 as in, heads that have been gone through, port matched, smoothed, ect..

    Thanks
    Mark
    I don't think the fuel will be much of a problem.
    start with CFM
    CID X RPM / 3456 = recommended CFM
    so
    392 x 4500 / 3456 = 510.4 CFM
    Now assuming you can turn your 392 to 4500 rpm and can achieve a .90 volumetric eff
    510.4 X .9 = 459.4 CFM
    A dual plane manifold and stock heads will be more restrictive so use a factor of about 1.3
    459.4 X 1.3 = 597 CFM actually needed.

    The more you do to improve your motor the more you can increase the VE. I really don't think a IH motor will achieve better than 1.0 VE
    VE=CFM X 3456 / CID X RPM
    If you do the math the 392 with a 600 CFM carb should be 1.17

    So what does all this mean to you....
    Well a good running 350 capable of about 5500 RPM has about the same CFM requirement.
    So I would say run your stock 392 on a 350 system and maybe upgrade to the 2 in(BBC) throttle body.
    And for a modified 392 run the BBC TB.

    I just did a 392 with the 350 system and it has good low and mid-range and good driveability but may be a little lacking on the top end. I am getting ready to swap a 2in TB on and see how much it helps the top end.

    HTH
    Bill USN-1

    COMMITED TO TEACHING PEOPLE THE "PROPER" WAY TO EFI
    HAMILTON FUEL INJECTION
    May be the answer to all your fuel injection needs!
    Learn to do it right.

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    • #3
      Thanks bill,
      Does the larger BBC TB have the same bolt pattern and everthing just the larger 2" holes verses the 1 7/8? for the sbc one I currently have.
      What can a bbc tb get picked up for anyway?

      Thanks
      Mark

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      • #4
        Everythings the same just the bore size and the injectors are bigger.
        complete on ebay they go for about $125 for a holley GM replacement or the factory GM TB. You can check with AFI and see what he has for just the TB and then bolt your 350 injectors on the top of it.
        whatch out for the older holley's, they don't have an IAC.
        Bill USN-1

        COMMITED TO TEACHING PEOPLE THE "PROPER" WAY TO EFI
        HAMILTON FUEL INJECTION
        May be the answer to all your fuel injection needs!
        Learn to do it right.

        Comment

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