Help! - Weber question

[gilbert911]

I posted a thread on the technical board but no one answered me - must have been too dumb a question to warrent a response

Anyhow do need some advice so I will try again here.
Please someone let me know.

I have a set of Weber 40 IDTP 3C carbs which are available to me and need to be rebuillt.

2 questions (see attached picture for question 1)

1) The 3 holes in the top (sorry for the non terminology) are approx 45mm dia.
Do the velocity stacks that fit on top have the same diameter??
Someone told me to get velocity stacks 42mm internal bore to fit the IDTP

2) Is the Weber 40IDTP 3C OK to use with a highish (210bhp) output 2.4 with S cams - which is being built for me now.

Open to suggestions but I need answers sooner rather than later

Many thanks Guys

[gruen911]

First of all, the Weber IDT3T carb's should work fine for your motor.

The velocity stacks (otherwise known as "venturis") do not have to be the same size as the carb intakes. I don't recall the exact size you would need for a 2.4S, but they are either 32mm or 34mm, and you can buy new ones from PMO for $80.00. They DO NOT need to have an internal bore of 42mm. Be careful who you listen to. My advise would be to get in touch with Steve Weiner at Rennsport. He will give you correct information.
To use these carb's on your motor, besides having them rebuilt you will also need to have the idle jets and main jets sizes changed (assuming these carb's came off of a 911T).

[gilbert911]

Hey a response! - thanks gruen.

Please see attached picture

Do this have to be 42mm ID or 45mm ID? to fit

[CamBiscuit]

Gilbert

I am running the same carbs on my 2.4 S cammed engine.

Specs are:
o Main Jet – 135
o Air correction 180
o F7 Emulsion Tubes
o Idle Jet – 60
Sorry I cant check the diameter of the velocity stacks, the cars is 3000km's away at the moment! I would assume they are standard size for the IDTP's
Velocity stacks are not the same as Venturis. VS"s sit on top of the carb body and venturis sit inside as per your top photo. I am running 32mm venturis in mine with good results.

Good luck

[gruen911]

Cam,
I think your emulsion tubes are way too small. I am pretty sure that the emulsion tube size on a 2.4S should be F3.

[gruen911]

Here you go. Who luvs ya?

[Steve@Rennsport]

Hey a response! - thanks gruen.

Please see attached picture

Do this have to be 42mm ID or 45mm ID? to fit

Gilbert:

Use the 42mm ones on your carbs.


Cam:

Emulsion tubes are matched to the camshaft in use as the hole diameters and positioning is designed around the intake vacuum signal. You ought to be using F3's as suggested.

[gruen911]

Velocity stacks are not the same as Venturis. VS"s sit on top of the carb body and venturis sit inside as per your top photo. I am running 32mm venturis in mine with good results.

Thanks Cam. I am a little rusty. Last set of carb's I had rebuilt was 2 years ago.
Part names get foggy for me after awhile. Must be age kicking in...

[gilbert911]

Steve,
Thanks for the consise answer.
Very reassuring

That's what I needed.

[CamBiscuit]

Whoops, I posted my old specs. I am actually using F7 Emulsions which are apparently quite close to F3's (according to PMO) Specs changed in post above.

Gruen, I'm 36 and have trouble remembering my own name some days!! Must be the 'hard living' in my youth catching up with me.....