Yet another Weber Jetting Question
 

I just installed 32mm venturis in my car. It was setup with 60 idle jets, 125 mains, 180 air corrector, f1 tubes and had 30mm venturis. The motor is a 2.2S.

After the installation of the 32's the car breaks up very bad under acceleration around 3,000. In normal driving the car runs perfect so I am thinking it is to lean with the 125's now. I am suspecting either I need to go back to 130 mains or the float level is low. Since I am a betting man I am going with the 130's. (I will check the float level as well).

Does my logic of the 130's seem to make sense?

Finally, I know I should probably be running F3 tubes so if anyone has some to sell please send me a PM.

Well I installed the 130's and checked the float level. The float level was correct so I just need to test drive it and see what happened.

I'm guessing the transition issues may be the emulsion tubes.

I have 55 idles, 32 venturis, F26 emulsions, 130 mains and 180 air correction, and the car is running quite nicely now. It had 34 venturies before and some mixture issues (fat down low, lean up high).

I have a similar set up, Smooth as a baby's behind and smells better too. Have you checked the fuel deliver from the pump jets?

I called Ron Flemming at FAT Performance a few years back and told him what my combo was (2.2, solex cams, 40ida's etc) he mumbled the combo back to himself and 5 seconds later he spits out

32mm venturi
55 idle
135 Main
195 Air
F3 ET

Right off it was super smooth.

I have since had to swithc to 65/145/200 to get it to run on this crapy mtbe gas we have out here in AZ/CA

PS: I think the fuel dleivery is suposed to be 0.5cc per stroke.

Keith:

You REALLY need those F3 emulsion tubes to work with your "S" cams.

I'd suggest contacting PMO or one of their dealers to get a set.

Remember, Weber emulsion tubes are precisely matched to each camshaft's manifold vacuum characteristics (duration) and you must use the correct one to make the transition circuits work properly.

I have not been able to drive the car yet to test it after installing the 130's. I hope to get to test it in the next few days. Thanks to the beautiful weather here it went from 65 yesterday to 20 now. UGH, I have Spring Fever and I want to DRIVE!


Steve - would switching to the 32mm's amplify a problem with transition? The reason I ask is that it seemed OK with the 30mm venturis. I am learning more about webers every day and my knowledge with them is limited. :) Right now the car seems to run very good at low speed throttle, will jump when I stand on it, but when it reaches transition to the mains it seems like it runs out of fuel. I guess as I type this I realize how the emulsion tubes would effect this; the larger venturis altered the vacuum signal. Well I will drive it and post my results. (and order some f3 tubes.)

Thanks for all of the input, I appreciate the help.

For some reason I thought the progression circut was someplace near 1800-2200 RPM that is why BA recomends adjusting the idle mixture at that point. I could be wrong. My wife tells me I am all the time.

Keith:

You answered your own question,....:)

Indeed, the reduction in vacuum from the larger venturies leaned out your engine. Installing the larger MJ's covered that up quite nicely except for the transition stage when the throttle is opened, the idle circuits are maxed out, and the main jet is not flowing quite enough fuel to prevent that flat spot.

Certainly, when the throttle is opened suddenly, the accelerator pump jets prevent a flat spot until the mains start flowing enough fuel and the emulsion tubes are what "accelerate" that process,...:)

Steve

Thanks for the information. I will hunt down a set of F3 tubes and see how that goes. I am always amazed at how much I can learn here!

OK one more dumb question, what is the best way to replace the emulsion tubes? Mainly, how can I pull the out once I get the air correctors removed? Is there a 'trick' way to 'suck' them out? Or am I better off pulling the carbs off, removing the tops and tipping the carb over? I have had the tubes out but that was when I rebuilt the carbs.

Keith - with the carb tops off, it is really easy to use a dental-pick type of instrument to gently lift the tubes out.

I know Richard @ PMO carries them, but unsure of the cost.

OK - The final word... I spoke to Richard at PMO and he felt my jetting is correct. When I explained to him what I did, he said he bet I had the secondary venturi's in wrong. Well he was right, 3 of the 6 were in wrong. I did not line up the venturi with the port by the emulsion tube. Well now the car idles at ~900, smooth as glass, pulls throughout the entire rev range to 7,500-7,700. Ah I love the wail of a short stroke 911!

Thanks to all your help the final jetting is:

Idle - 60
Main - 130
A/C - 180
Emulsion tubes - F1
Venturi - 32mm
Secondary venturi's NOW INSTALLE CORRECTLY! :o

Now you have no excuses not to track it....come out to Test and Tune?

Glad your "Gem" is running well.... :)

Souk, that is the plan, get the car on the track this summer.

Keith:

Did you just forget to post the G-Tech numbers or are you keeping it a secret to surprise the locals?

Rich

PS-- Once again many kudos to Richard at PMO. His recommendations have always been right on the money and he has my business.

I figured I would wait for the local run at RT66 to back up the G-Tech data. ;)