Webber IDF 40s, Help with tuning Options

[Chad911sc]

So I finally finished every aspect of my restoration and I’m on the final step before really being able to break my new 2056 in. I have the idle circuit close enough to where it needs to be with idle jets of 50. My problem is my transition from idle circuit to the main circuit. I had purchased a set of Gene Berg venturis that were a 30 idle circuit and then with wide open throttle they would increase the flow to 34. I thought this would be good with better flow at the top due to the web cam (86a) which is supposed to be more mid and top range power. I have ported 2.0 heads and 96mm pistons and cylinders. It also has the 123 distributor set on setting #3. The timing is set at 5 degrees base timing and 28 degrees total.
The problem is that if I even try to open the throttle more than an inch or so, the AFR gauge slams over to 16 or higher. So I’ve only driven it a few times after adjustments, and it does the same thing everytime.
I took out the fancy dual plain Venturis and put in a set of stock functioning 30 vents and just took it for another spin. It does the same thing with the 30s.
Current set up:
ET F11
Idle 50
Mains 130
AC 180
Vents 30
My float level is set at 10.5 with the gasket.
I’m at sea level in Florida.
As long as I just ride the pedal gently, the AFR stays in the 12-14 range all the way up to 4000 rpm. It idles at 10.5-11.5.
The carbs have been rebuilt and are synced and balanced.
I am ordering a set of AC and mains so I can adjust further as needed.
Should I try to go down on the air correction jet first to fatten it up on the top?
Or maybe something different with the float height to provide more fuel in the bowl?
Thanks in advance for all your advice. Can’t wait to be able to run this thing!!

[Chad911sc]

Perfect…
Excellent idea. I will change those out in the am and see what results I get. There is so much information out there that contradicts itself. So many ways to tune and get to the desired results. I have read so many posts that lean towards the 28 vents on a 2056. Then the people who make the parts (Webber), say that I should be running a 32 vent with cam and heads. So I settled in the middle at 30 after removing the fancy dual plain ones.
Will report back tomorrow with the feedback.

[Superhawk996]

Perfect…
There is so much information out there that contradicts itself. So many ways to tune and get to the desired results. I have read so many posts that lean towards the 28 vents on a 2056. Then the people who make the parts (Webber), say that I should be running a 32 vent with cam and heads.

The interesting thing about carbs is there is usually more than one way to achieve an outcome and sometimes one of them will be counter intuitive - like going to a smaller Venturi.

Keep in mind that much of the advice you’ll get on carbs is aimed at maximizing horsepower . . . Even if that means diminished drivability.

I post this chart often - it’s is a pretty common set of curves that aligns well to recommendations both in the Weber tuning guide as well as several of the published tuning books for Webers and Dellorto’s.

The thing is - this chart is for HP. If you use this for tuning street drivability the tuning will suck due to picking a Venturi that is way too large (like 34-36 mm). I know . . . Cause when I was young I thought I wanted to maximize HP. But it turns out - we don’t drive around on the street at redline. Go figure. Took me a lot of years to learn this the hard way.


And here’s the one from the Weber tuning guide


When tuning the first thing to pick is the Venturi - that sort of determines everything else. And if the Venturi is too large, you don’t get a good vacuum signal and everything else sort of goes to (IMG:style_emoticons/default/stromberg.gif)

As a generalization: People over-carburate and then wonder why they have poor drivability. I had to learn these lessons myself the hard way.