I just installed a fresh 2.0L in my 912E. The car had a 1.7L with 40 IDF carbs, and allways ran very rich. My jets are as follows:
Main 125
Idle 50
E tube F11
Air 200
Is this even close?
Thanks, Rob

I've got a 912E (#265) with a 2056 and two 40MM Webers. The venturies have been enlarged and I used whatever Jake told me . I think I have 140 M and 55 idle but my venturi is a 36MM i think. See if Jake responds ....do as he says.

100%! Since you went up 300 cc's, & were running rich, I would leave it where it is & start tweaking from there.

I followed Jakes pattern as well. Get a mallory dizzy if you haven't already.
my 2.0 is perfect with 40 IDF using 28mm vents
120 main
50 idle (use 55 if it cruises hot)
180 air correctors (200 made mine hot at extended high rpm)
I've got the taller CB's style manifold with 1.25 in velocity stacks.
Throw in a webcam and ssi exhaust.

zoom.

my 2.0 is....
44 webs,
34 vents
135 mains
55 idles
200 airs

What cam and CR in the 2.0? stock? I would think you should be pretty close. Maybe a hair on the lean side?

Why would going up to 55s in idle and going smaller in air correctors (180) make your engine run cooler? I can see that the idle jets would give you more fuel... which might make it cooler? Why would error correctors make the difference? Interesting... My car runs a little warm on the freeways. I just added an oil cooler but it would have been MUCH easier to change jets. = ) Just want to make sure I understand.

Thanks.

Eric

When you run lean you run hot. AC jets mostly affect your top end (high velocity flow). The smaller the AC jet the more restrictive it is. As you restrict the air you draw more fuel from the mains. If you increase your AC size you do the opposite.

Pat Braden has a great book on Weber carbs. He goes over all the circuits, jet selection, tuning, troubleshooting, and rebuilding.

According to charts, published by Weber, the main jets should be 4 X Venturi size. Example - 32mm vents = 128 mains. Air Corr jets should be mains + 60 = 188.

Idle jets are determined through troubleshooting and driving characteristics. I went through 50, 55, and finally settled on 60 idles.

My 1911 set-up with Italian Weber's are such:

Vents - 32
Mains - 130
Air Corr - 190
Emulsion - F11
Idle - 60

I've got a bit of fluffiness at 2800 rpm so may be trying new mains.

The F11 was designed to reduce high velocity enrichment (lean it out). Running AC jets above 2.00 with the F11 increases this effect even more. You "fluffiness" could be an ignition issue or it could be your ET selection.

Interesting. I'm running a Mallory Unilite from another car that had no issues. So I suspect the ignition is just fine.

What ET would you suggest?

(sorry to hijack)

Your idle jet is oversized. I would think a 50 would be perfect and a 55 would be on the rich side. I suspect you bumped it up because you had lean transition issues. If you float level is correct try an F9 ET. It was designed to enrichen the mixture at lower velocities. Tables and calculations in the tech books are great for getting you in the ballpark as far as jet sizes go. They don't take into account what ET your using. ET's have different quirks and were designed for different applications. Check out all the available ET's and what they do for you. Also look into your accelerator pump. Some lean transition issues are due to undersized pump jets.

As far as the original question in this thread. I would have started with those exact same jets.

I agree, I started out with 55 idle jets and found them to be just a bit too rich. I could not get too much of an adjustment with 55's in, so I switched to 50's.

I installed a 2056 in December and am running Weber 40 idf's as well. My jetting is as follows:

36mm venturies
F11 emulsion tubes
130 main jets (Oxygenated California gas)
180 air (San Diego, sea level)
50 idle

I did have some bugs to work out, such as float level adjustment... and also found an issue after the install ~ my needle's were worn where they seat. I replaced them and the car has run very well since.

Your numbers seem like they should work for you for where you live... what venturies are you running?