Need help - Strange Webers IDF 40 ?!?!

[beetlepowerpt]

Hello just tell me what you guys think about these one's....they are to be fitted to my 1835 W120 40X35 009 distributor...Needing some help!!!!!I have read lot's of info (MHarney's too ) but just need a little more whith these ones!LOL

I think they came originally from an Alfa 33 1300cc's engine.I just replaced the starter choke assembly whith a block-off plate(does it need some sealling compound or gasket or just bolt on?).
The body states they're IDF's 40, they have 28mm vents and jetting figures are 50 idle, 122 mains on F67 tubes?!?!?! and 190 air correctors....
Adicionally there is no air bypass screw that location is factory sealed, just on the other side of the idle mixture screw there is some kind of vacum tube(should it be closed?).
Basically I think I need to change everything!?!?! lollolol

[mharney]

Certain 40 IDFs came similar to the 36 IDF with larger air bushings, internal mixture screws and 5 larger progression ports. These models also had F67 emulsion tubes.

Basically you can either jet it as it is, or you can switch to F11 emulsion tubes. The jetting is different on these.. larger idle jets, and large main/air combinations work better with the F67 tubes. F11 jetting is difficult, and to get best results, modifications to the carbs may be needed. I'd say go with what you have first and see what you can do with it.

[beetlepowerpt]

So do you think the F67's are a good choice to try on the VW?
What jetting baseline should I aim to at sea level for my engine specs with the F67's?

[mharney]

Your carburetors are different from typical IDFs made today. The emulsion tubes will mostly affect the main circuit, but transition is affected too. 60 idles, 135 mains, 220 airs is a good start.

If you want to use F11s, 60 idle, 125 mains, 200 airs is where I would start. These carbs have to be jetted a little bigger.

[beetlepowerpt]

Ok Harney thaks.

And what about the 28 vents are they ok for the aplication?
Should I maintain the float level settings as usual with these ones?

[mharney]

The vents are small for your engine. I think I'd use 30's or 32's. I don't know anything about the heads, other than the valve sizes.. are they ported or just out of the box? How do you want to drive it?

[beetlepowerpt]

Yes the heads are Magnum 40X35,5 long reach spark plug ported, with matched CB manifolds.Cr was built to 8,5:1 just because what almost everybody says about 92's getting hot.
The car is not a daily driver, is to be used on weekends as a road car and see track use on trackdays once a month or so.

[mharney]

Well, for power and cooling they're probably not the best choice, but they'll do ok. 32 vents are probably what I would recommend. With those, you'll probably have some transition weakness, as those particular models already have earlier departure of the idle circuit. Bigger jets will help. I'd start with 145/220 on the F67s and see where you need to go from there.

[beetlepowerpt]

Ok Harney thanks again.I will check the spare carbs of my friend to see if there are any parts interchangeable.
I'll aim for your setup and after I try it will post the results

[70gmc402]

You can probably pop off those plugs covering your air bypass screws - usually just an aluminum or lead cap was installed to prevent "fine tuning." Just back as*ward if u ask me. Poke them with a sharp awl in the center and wiggle or twist them out.

[beetlepowerpt]

Hello guys,

I tried the settings Harney recomended I they're good enough.
But as he said maybe going on 32 vents woud help also, whith that in mind I was thinking on changing the vents and came across this on www.customspeedparts.com:

"Weber IDF Update Kit

Power up your Weber's with this new IDF Update Kit. The IDF update Kit features horizontal spray bars that replaces standard bulls eve secondary venturi to produce improved atomisation through the power band. Longer taper flow 34mm main venturi to improve air flow and special calibration are also included. Each Weber update Kit also includes a complete gasket and O-Ring kit. IDF Update Kits are available to fir 40 and 44 Weber IDF Carburetors. Each kit is designed to convert two carburetors to fast track horizontal spray bar discharge. This is a straight forward parts replacement installation. Machining, drilling or altering of the carburetor is not required. "

What do you guys think about these?
Should I buy the 32's or go for the update kit with 34's?

Thanks

[modok]

My apologies for necromancing this thread, but for future reference.

The cb update kit does not fit, and is completely not needed, since these carbs are the same top diameter as a 44 IDF. They use 44idf or empi HPMX type vents and aux. vents(nozzles).

The carbs have 3.5 aux. vents, instead of the normal 4.5
4.5 is usually preferred when using vents on the larger side

Another thread on these carbs: http://www.thesamba.com/vw/forum/viewtopic.php?t=535498

[MitchS046]

Hey guys,
I’m currently rebuilding the same carbs for my 1600 (ported heads, tcs-20 cam, and there will be a turbo in the future) and was wondering how they held up through the years? And if your opinions chaged about f11 vs f67. Also how did you guys block of the fuel return port?

Thnx
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