Weber Carb Restore Questions, Manifold preferences, Manual Choke, etc.. Options

[Literati914]

I'm going to restore (try to) a set of Italian Weber 40idf carburetors to put on a 1.7 engine. I have two sets of manifolds... one set has a vacuum port on one runner (each side of engine), and the other has none at all. Is one type favored?

Which do I want to use, and why? - I have no idea what the vac ports would connect to. If they help even out idle, I'd want them I guess. Thoughts?

[dtmehall]

what kind of distirbuter?

[Literati914]

what kind of distirbuter?

These are bigger ports on the manifolds than typical of a vacuum port on a distributor.. (IMG:style_emoticons/default/idea.gif) But to answer the question, I have not really thought about it - I do have a Pertronix Flamethrower SVDA in a box somewhere, so probably that.

[porschetub]

the inlet manifolds you describe with the large vacuum fittings would have been used on a t4 VW bus most likely ,they are there for power brake servo so not needed the plain ones will be fine on a 914.
Pick up vacuum from one carb with the SVDA dizzy and you will be fine and block off the unused one on the other carb ,just make sure the carbs have 28mm vents and moderate jetting for a 1.7 otherwise it will run like (IMG:style_emoticons/default/stromberg.gif) ,cheers.

[930cabman]

[quote name='Literati914' date='Aug 5 2026, 07:13 PM' post='3267680']
I'm going to restore (try to) a set of Italian Weber 40idf carburetors to put on a 1.7 engine. I have two sets of manifolds... one set has a vacuum port on one runner (each side of engine), and the other has none at all. Is one type favored?

Which do I want to use, and why? - I have no idea what the vac ports would connect to. If they help even out idle, I'd want them I guess. Thoughts?
[/quote

my first thought is, too much carbs for a 1.7?

I am running a set on my 2056 and are working very well. Too much carb volume is generally not good. Maybe source a set of early single throat carbs

so far as the rebuild process, it's like anything else, do your research, take your time, measure twice (or more) cut once

[dtmehall]

i am running 40idf's on a 1.7, and it runs great!

[Literati914]

the inlet manifolds you describe with the large vacuum fittings would have been used on a t4 VW bus most likely ,they are there for power brake servo so not needed the plain ones will be fine on a 914.
Pick up vacuum from one carb with the SVDA dizzy and you will be fine and block off the unused one on the other carb ,just make sure the carbs have 28mm vents and moderate jetting for a 1.7 otherwise it will run like (IMG:style_emoticons/default/stromberg.gif) ,cheers.

Thanks for the info.. the pic below shows the large vacuum ports I’d mentioned. So I suppose if I pull a single vacuum from my other manifolds as you suggest, I’d need to tap in a small nipple for it? - I haven’t seen that before.

[Ninja]

You will want the smallest venturis available for that.

Pierce Manifold is my go-to for Weber stuff.

They should have 27 or 28s available.

I'd start with 135 mains, 200 Airs, and 50 or 55 idles.

40 IDFs with 28 venturis are excellent for 2.0Ls with a "street" friendly motor.


Manifold ports don't matter, just make sure to cap them off.

Those might be helpful if you were going ITB fuel injection as they could form a plenum for an IAC (idle air control) valve.

[Literati914]

You will want the smallest venturis available for that.

Pierce Manifold is my go-to for Weber stuff.

They should have 27 or 28s available.

I'd start with 135 mains, 200 Airs, and 50 or 55 idles.

40 IDFs with 28 venturis are excellent for 2.0Ls with a "street" friendly motor.


Manifold ports don't matter, just make sure to cap them off.

Those might be helpful if you were going ITB fuel injection as they could form a plenum for an IAC (idle air control) valve.

Good real world info right there, thanks

[dtmehall]

i am running 52 idles and 125 mains

[dtmehall]

and 28 mm venturis

[Literati914]

i am running 52 idles and 125 mains

and 28 mm venturis

(IMG:style_emoticons/default/aktion035.gif) Thanks for the specifics!

[porschetub]

i am running 52 idles and 125 mains

I'am a Dellorto guy but that sounds about right ,28mm vents provide great vacuum signal and response to assist early transition to main jets which IMO work well on a small displacement T4 .this will work well with the svda Pertronix dizzy you have.
You will be drawing vacuum from one carb and not the manifold as you need a vacuum that is variable due to throttle position so the undrilled manifolds are your best choice as you mentioned you had a set .
Cheers.