Modified Weber IDS carbs

[1QuickS]

For a customer with a FIA, 1967 911S, Sports Purpose car from the factory I modified a set of 40IDS Webers for racing. I do not get a chance to do this very often so I post this for viewing pleasure.

Details of modifications:

• Thinned throttle shafts with low-profile fixing screws
• knife-edged throttle valves
• 906/911R throttle lever arms (shorter than OEM)
• Fuel floats reinforced to prevent bending
• Tall auxiliary (booster) venturis
• float well baffle plates
• High Speed Enrichment Tubes "adjusted" to clear the tall aux venturis
• Emulsion well air screens which include reduced openings where the vent pipes were installed
• Weber IDF accelerator squirter nozzles
• idle air correction jets reduced to 0.90mm from 1.10mm
• IDTP style accelerator cam lever arms

The customer will install full-radius air horns with screens. Maximum main venturi size is expected to be 37mm which is possible due to thinned shafts decreasing flow blockage.

[edmayo]

Nice work Paul,,,,you should consider starting a business!! By the way, I guess the shorter arms were to decrease throttle pedal travel, but why would they do that? Seems like it would be more of an 'on-off' switch effect?

[targatuesday]

If carbs can be sexy, then these are some sexy carbs!

[1QuickS]

The short lever arms were requested by customer as a period piece for dedicated track cars which is what these are for. They were OEM for the 46IDA3Cs as used on 906, Carrera 6 & 911R plus the Sports Purpose 911s, 914/6 GT & the 2.3 liter 911STs. Yes, more like a "toggle switch" for throttle application than the standard length lever arms. The original car was outfitted with a 901.20 engine with 46IDA3C Webers but FIA will not allow those today so 40IDS3Cs were selected for use and tweeked.

Maybe I could/should start a carb business, if only I could get someone to express confidence in my work. (Ed, you did express confidence in me when I started out and I remain grateful for that!)

[JackMan]

Paul, those webbers are almost as beautiful as the ones you did for me . You do phenomenal work. FYI: Paul customized some 40IDS3C1's for my 67 911 bumped to 2.2l with 2.7l heads. His knowledge and craftsmanship is impeccable. Update: the chassis is almost finished, just installing a new floor pan then to primer and paint.

Wj

[ajwans]

Wonderful Paul, thanks for sharing. Could we see the throttles if you have pics please?

- andy

[H-viken]

Nice! Thanks for sharing!

Full radius air horns - is there any evidence that they work better than the originals? I’ve heard both but have never seen any data for or against

[gled49]

+1, keep up the good work. Gordon

[1QuickS]

I used full radius (nearly full radius) horns on my 2.3 S-cammed engine. I had a persistent 3000 RPM flat spot that I could not jet around. I tried idle fuel jets, idle air jets, emulsion tubes & main air & fuel jets...nothing. Then, I installed the new horns and wasn't expecting anything and a bit later I realized the flat spot was entirely GONE! As for power, I have read technical documents that compare various horns including a straight pipe, tulip (like the Webers use), full radius and elliptical. Full radius & elliptical profile horns do add power improvements

I provide link to the best article regarding intake horns I have found.


http://www.profblairandassociates.co...mouth_Sept.pdf

Below is picture of my engine with "full radius" horns, I used K&N air cleaners.

[Bullethead]

Nice! Thanks for sharing!

Full radius air horns - is there any evidence that they work better than the originals? I’ve heard both but have never seen any data for or against

Here's a sheet showing flow efficiencies from David Vizard (muscle car engine tuner, Holley guru but physics is physics)... note the most efficient radius. Paul just convinced me to change mine.