Installation of weber 40 IDTs

[leedurrant73]

Hello,

I resently removed my of zeniths as they were past there best and found a great set of overhauled weber 40 IDT's, I'm running a standard 2.2t engine except for a twin outlet stainless
exhaust, new resently installed SSI's and slightly ported / polished heads.

Would the weber 40 IDT's provide any performance improvements or HP?

Thanks for your help,

Lee

[1QuickS]

Weber IDTs have only one variance from IDAs; the first progression hole is 1.00mm vs. 0.80 for IDAs. As such the IDTs will provide the same performance potential as an equivalent IDA. The ability to select the main venturi diameter and emulsion tube of choice is what makes Webers nice to have, Zeniths have only one main venturi and one emulsion tube to select from unless you acquire aftermarket parts.

Your Zeniths probably came with 27mm main venturis and the Webers could easily be upsized to at least 30mm unless they already have them installed which is what the 1968 911T (European market only) would have been delivered with. This would increase top end performance a bit over the Zeniths.

[John912]

Lee:

I'm running 40 IDTs in my 71 2.2 T -- can't compare to Zeniths because I never ran them. I believe original IDTs originally came with 27 venturi, 110 main jet, 185 air correction jet, and 50 idle jet. Check what you have. Others with more experience will let us know what's the best setup for 2.2. My IDTs have standard setup except for 30 venturis and 45 idle jets.

[leedurrant73]

Lee:

I'm running 40 IDTs in my 71 2.2 T -- can't compare to Zeniths because I never ran them. I believe original IDTs originally came with 27 venturi, 110 main jet, 185 air correction jet, and 50 idle jet. Check what you have. Others with more experience will let us know what's the best setup for 2.2. My IDTs have standard setup except for 30 venturis and 45 idle jets.

Hello Jon,

I have 27 mm venturis, 185 air correction jet And 50 idle jet so looks standard.
Woul appreciate anyone's thought on performance...

Cheers lee

[1QuickS]

Yeah, John912 is correct; 27mm venturis were OEM, my mistake.

I have a customer with "Happy Jetting" in his 2.2T; he confirmed good jetting using AFR data:

• 30mm main venturis
• 125 main jets
• F3 Emulsion tubes
• 180 Main air correction jets

[leedurrant73]

Yeah, John912 is correct; 27mm venturis were OEM, my mistake.

I have a customer with "Happy Jetting" in his 2.2T; he confirmed good jetting using AFR data:

• 30mm main venturis
  
• 125 main jets
• F3 Emulsion tubes
• 180 Main air correction jets

Hello Paul,

Thought I would catch up with you and ask your thoughts with jetting my carbs correctly,
A few changes to my set up now and running solex cams with s type p & c's. had the distributor curve
changed also. Running SSI's with stainless twin outlet dansk exhaust. Apart from that a standard 2.2t
Engine so a little more power, bro ably about 155 bhp estimated.

I recently rebuilt my IDTP carbs and wondered if I should change anything to make them run correctly.
27mm Venturis.
185 air correction jet.
50 idle jet.

Hope you can help.

Regards Lee

[leedurrant73]

Hello Paul,

Thought I would catch up with you and ask your thoughts with jetting my carbs correctly,
A few changes to my set up now and running solex cams with s type p & c's. had the distributor curve
changed also. Running SSI's with stainless twin outlet dansk exhaust. Apart from that a standard 2.2t
Engine so a little more power, bro ably about 155 bhp estimated.

I recently rebuilt my IDTP carbs and wondered if I should change anything to make them run correctly.
27mm Venturis.
185 air correction jet.
50 idle jet.

Hope you can help.

Regards Lee

Can anyone help ?

Thanks Lee

[1QuickS]

Hi Lee,

I just today completed a back-to-back running comparison between a set of IDTP Webers and a set of IDA Webers; both remanufactured by me and using 34mm venturis. I ran them on my 2.3 S-spec engine which is currently fitted with a twin pipe Dansk sport muffler. I fussed with the jetting on the IDTPs to get them as good as possible with the result they seem to be comparable with the IDAs except for a little stumble during a roll-on at 3500 to 4000 RPM. I think the IDTP stumble could be adjusted out with more accelerator squirt or possibly using F24 E-tubes.

AFR readings were below 14 at WOT and mostly in the 10's to 12's during "normal" running. I couldn't get the jetting leaner without getting lean response issues.

IDTP jetting:

• 34mm main venturis
• 130 mains
• F3 emulsion tubes
• 160 air corrections
• 52 idle jets
• 120 idle air bleeds (OEM are 140)
• standard length auxiliary venturis

IDA jetting:

• 34mm main venturis
• 145 mains
• F3 emulsion tubes
• 170 air corrections
• 55 idle jets
• 100 idle air bleeds (OEM are 110)
• tall auxiliary venturis

The idle/progression was a little rich on the IDA carbs so a 52 idle jet and a 110 idle air bleed would correct this.

For a 2.2 with Solex cams I'd suggest:

• 32mm main venturis
• 135 mains
• F3 emulsion tubes
• 160 air corrections
• 50 idle jets
• 120 idle air bleeds (I make a modification kit for this; contact me via my web email address)

Hope this gets you close :-)

Paul

[leedurrant73]

Sorry for delayed response Paul I'm on holiday appreciate your time and effort.

Kindest regards,

Lee