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Technical ISO a Weber carb genius.

Discussion in 'The Hokey Ass Message Board' started by Nitro450exp, Aug 2, 2020.

  1. Nitro450exp
    Joined: Dec 26, 2018
    Posts: 21

    Nitro450exp

    Picked this up, want to use it on a 327 to 350 SBC 8:1, 4-71 at about 8 psi. The idle circuits and main jet circuits are missing ( no biggie I figured I would need to rejet anyhow)
    Looking for Weber guru who can reccomend main jet sizes, emulsion tube sizes, idle jet sizes, accelerator pump jet sizes float seat etc.
    I will probably get a jet kit, but it only comes with mains and idle jets in 8 incremental sizes, so I need to be close on the other sizes before trying to dial in the final jetting.
    Carbs are Italian made Weber 40DCOE32 models.
    Can they work on a blown mild SBC or do I need to step up to 45mm or 50's ?
    THANKS
    Nitro 20200801_121826.jpg
     
    loudbang likes this.
  2. Nitro450exp
    Joined: Dec 26, 2018
    Posts: 21

    Nitro450exp

    This is what was standard in the 40DCOE
    But probably for an 1800cc to 2000cc 4 cyl Alfa.
    s-l400 (1).jpg
     
    loudbang likes this.
  3. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,627

    gimpyshotrods
    ALLIANCE MEMBER

    That's about 1/2, or less, of what you wound need for your application.

    I have fairly routinely installed two 40s, and eve 48s on air-cooled VWs.

    This is a 348:
    eight twos.jpg

    Not one of mine, but it shows how many can be used.
     
  4. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,627

    gimpyshotrods
    ALLIANCE MEMBER

    Dual 40s are customarily found on 1.6l to 2.0l 4-cylinder engines.

    A 289 Cobra had four 48s, and no blower.
     
    loudbang, Hnstray and TrailerTrashToo like this.

  5. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,627

    gimpyshotrods
    ALLIANCE MEMBER

    The biggest benefit of the Weber (and similar) carburetors of this type is their IR (individual runner) design. Each barrel services a single runner, to a single cylinder, for maximum efficiency.

    Once you dump all of that into a supercharger, that benefit is void. At that point, you are just in in for the look.
     
  6. Inglese's website shows a couple of setups with 2 weber carbs on top of a blower (4-71), so it seems like it's doable. There's no information beyond the images, but an uneducated guess is that it goes on top a pretty small engine with low boost.

    twin_chrome_idf_1.jpg blueonpoldcoe.jpg

    They also have an intake for 4 carbs on top of a blower.

    supercharger_4_dcoe.jpg

    I agree with gimpy that it's just for looks... but it's a pretty cool look (well... the blue finish, not so much). :)
     
    loudbang likes this.
  7. Phil1934
    Joined: Jun 24, 2001
    Posts: 2,713

    Phil1934
    Member

    B&M offered 2 40s on their 144 as there is a big demand difference between plenum and individual runner
     
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  8. nrgwizard
    Joined: Aug 18, 2006
    Posts: 1,222

    nrgwizard
    Member
    from Minn. uSA

    Gimpy is right, & the IR effect is destroyed if these are used on a plenum also.
    Marcus...
     
  9. Nitro450exp
    Joined: Dec 26, 2018
    Posts: 21

    Nitro450exp

    1 tube feeding 1 runner, but with blower and single plane I essentially have 4 tubes feeding 1 runner at a time.
    I actually think a 45 or 48 is too big, that is why they chose 40's
     
    loudbang likes this.
  10. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,627

    gimpyshotrods
    ALLIANCE MEMBER

    That's part of a BDS setup that used FOUR 40s.

    Two might be fine, for a 4-71, on a small flathead.
     
    loudbang likes this.

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