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Thread: Holley carb CFM

  1. #1

    Default Holley carb CFM

    What is the CFM for the Holley that Ford put on the 2.3? I'm thinking of fabbing an adapter to mount two, 2V's on a 289 using a 5.0, lower FI intake plenum. The two would both fuel continuously as opposed to a primary and secondary carb and would be mounted with the venturi in a straight line, not 2x2, with the throttle shafts inline with each other. The 2.3 Holley would be ideal since I wouldn't even have to modify the direction of the throttle lever action.
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    Last edited by rose62; 09-11-2017 at 07:03 PM.

  2. #2
    FEP Super Member xctasy's Avatar
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    Jun 2012
    Dunedin 9011, New Zealand, South Pacific


    Holley Weber R6503, the 5200 version for Fords

    Weber 32-36 DGV Manual Choke

    Chapter 4 SOHC Pinto Carb Modification, Weber 32-36 DGV Manual Choke

    Rated pressure drop stated as 25 " H20, but actually 1.83" Hg----->Industry Standard varies.

    Holley Webers 5200/6500 for non turbo instillations were further down graded to 23 mm primary venturis, so 1980 to 1982 ones flow even less than the figures above.

  3. #3


    Too small. Thanks

  4. #4


    Be sure to give yourself a common vacuum reference or it could become difficult to tune...

  5. #5


    Please explain, 50

  6. #6
    FEP Super Member xctasy's Avatar
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    Jun 2012
    Dunedin 9011, New Zealand, South Pacific


    If its cfm you want, then the 32/36 DGV has a big brother, the 38 DGES Webers, which are 300 cfm at 1.5" Hg, 29 mm venturis, open both at the same time, and you can manual choke them. It was used from 1972 to 1981 on UK 3 liter V6's giving 138 hp, as well as the South African P 100 utes till 1994.


    1. tips in towards each barrel, and

    2. is a great carb.

    3, its also shallow, so it should fit "under the hood".

    There is no bad air fuel distribution with it, and parts are good. It'll need a pressure regulator to take psi down to 2.5 to 3.5, without loosing flow to the carbs.

    a '94 900S 2.5L non-turbo hatch from Arizona with twin 38's

    Price wise, its hefty, but its long lasting and doesn't have float problems or tuning issues as long as you use a good PCV valve that isn't hooked to any part of the carb. It has to follow the normal V8 path

    The earlier version used in Limey Zephyrs and Capri GT and GXL 3000's was a Weber 40 DFVA, a not very reliable carb, but it flowed 342 cfm with 29 mm venturis, or 311 cfm at 1.5"Hg, only 11 cfm more than the newer Weber.

    Off road Jeep guys and SLant Six and 24/26/28 0z Datsun guys use the 38 DGES Webers, they can be snaffled up from Vintage inlines, which sells a base plate for direct mounts to in line sixes.

    On a 289, rated at 1.5" Hg, that's still 622 cfm, enough for almost 390 flywheel hp.

    1.5"Hg -----> 20"H20
    1.83"Hg ----->25"H20
    2.0"Hg -----> 28"H20 (27.2 really)
    3.0"Hg -----> 40"H20

    Holley 4bbls, 1.5"Hg
    Holley 1 and 2-bbl, 3.0"Hg
    Holley Weber 2-bbls, 3.0"Hg
    Some Autolites were reputed to be rated a 2"Hg, BUT I doubt this, its normally 1.5" for 4-bbls, and 3.0"Hg for 1 and 2bbls.

    To convert, the square root of the difference.

    These are rated at 1.83"Hg ----->25"H20 by David Vizard "Carb Education" "Weber Carb Edjumakashun"

  7. #7


    "Some Autolites were reputed to be rated a 2"Hg, BUT I doubt this, its normally 1.5" for 4-bbls, and 3.0"Hg for 1 and 2bbls."

    Is this due to the difference in velocity between supplying an identical number of cylinders with a different number of venturi?

  8. #8


    Brief examples given

    A full vacuum line at the base or bung in each runner (either one) connected to a distribution block would allow for reference across all cyl and ensure adequate vacuum for brakes, etc. Also makes it easier to tune because you can see a vacuum reference across the entire engine. Multicarb sync tools help too of course.

    Just thinking back to fighting with the 4 carb setups on some of the bikes I've worked on.

  9. #9


    I always wanted to do an inline four barrel setup using two 500 cfm Holley 2305 carburetors. The 2305 is identical to the standard 2300 two barrel but the throttle linkage is on the "back" side and each barrel has it's own throttle shaft, mechanically linked. Two 500 cfm two barrels is equivalent to a 750 cfm four barrel. Unfortunately, the 2305 carbs are pretty rare and demand a premium when they do surface.

  10. #10
    FEP Senior Member
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    Jan 2011
    Vancouver BC Canada


    Sures seems to be an awfull lot of bother for no reason. The EFI lower has no plenum area, I would bet that even something mild like a 600 Holley on a Perfromer intake would do everything better.
    1978 Fairmont 2 door sedan, 428CJ 4speed. 9.972ET@132.54mph. 1.29 60 foot
    Replaced the FE big block with my 331/4 speed in my Fairmont, best 10.24ET @128 MPH.
    1985 Mustang LX hatchback NHRA Stock Eliminator 302 4 speed best in legal trim 12.31@107 mph, but has gone 11.42@115 with aftermarket intake, carb, and iron Windsor Jr. heads.New for 2012! 331 cube SB Ford, AFR 185 heads, solid flat tappet cam, pump gas; 10.296ET@128.71 mph, 1.37 60 foot.
    1979 Zephyr Z7, all original 302 auto, 2nd owner.

  11. #11


    Might be better off with a box plenum that is side fed

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