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!!

[densible1]

I'm also at sea level with my 2270 (2256) build utilizing 96mm cylinders/pistons. I'm using 44's idf because of the longer stroke. After much trial and error I ended up with this configuration which keeps air between 11.5-14 bout 12 at idle .
Vents=36
AC=200
Mains=135
idle=55
Also 123 is 5-7 dynamic advance but up 32 advance starting at or above 4000rpm. Throttle response is smooth throat power band. Perhaps ending up with 36vents could mean that a vent bout 8mm smaller than the idf size might be a good guide.
Mark

[densible1]

Wait, correction I meant 5-7 static advance on the bluetooth 123

[Chad911sc]

After re-reading my post I forgot to add that the fuel system is all new and I have 3lbs of fuel pressure at the carbs.

[Superhawk996]

How about some homework?

Suggest you read this thread. Take note Brent was at about 6000 feet but the tuning principles are the same. Just know you’ll run slightly richer jetting at sea level. I’m going to put forth the following proposition: unless you really want the absolute last 5% or so of top end horsepower and are willing to trade driveability for it - 28mm venturis may serve you better.

http://www.914world.com/bbs2/index.php?showtopic=359926

Hint: IDF’s are running on the idle circuit far more than you think - especially at the part throttle transition you’re having problems with.

Interesting fact: you can drive the car pretty well at partial throttle, on level ground with the mains and emulsion tubes removed. (Don’t do this in rush hour traffic (IMG:style_emoticons/default/laugh.gif))

Read the section on the idle circuit and transition ports. page 10.

https://www.lainefamily.com/images/WeberTuningManual.pdf

[Chad911sc]

I still have a set of 28 vents, so that is an option.
I will read the posts that you have provided and see if I’m missing something.

[Chad911sc]

So after reading the material you sent me, I thought it would be a good idea to check where all my screw settings were adjusted. I read the CB performance low circuit running and it took me step by step through the tuning process again. The steps that I followed the first time were very similar, but not exact. After following their method, the engine sounds like an angry bee when I rev it. Wow what a difference. The AFR at idle is now 12.5 fairly steady and hums at 850-900 idle speed. Starts very easily now as well.
I will take if for a spin tomorrow and report back any issues.

[Superhawk996]

(IMG:style_emoticons/default/smilie_pokal.gif)

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[930cabman]

So after reading the material you sent me, I thought it would be a good idea to check where all my screw settings were adjusted. I read the CB performance low circuit running and it took me step by step through the tuning process again. The steps that I followed the first time were very similar, but not exact. After following their method, the engine sounds like an angry bee when I rev it. Wow what a difference. The AFR at idle is now 12.5 fairly steady and hums at 850-900 idle speed. Starts very easily now as well.
I will take if for a spin tomorrow and report back any issues.

Webers can be tricky, but when dialed in they sing

glad you got them happy

[Chad911sc]

After the test drive today, it is tuned better than before, but still leaning out if I try to push anything into the throttle. If I drive it with a very gentle pedal, it stays in AFR 12/14. Anything else than light pedal it falls on its face and leans out to 16 or higher, but I don’t obviously stay in it.
The idle screws are right at a half inch in after making contact.
The mixture screws are anywhere from 1.5-2.2 turns out.
It is leaning out with any type of pedal, so does this mean that I need to go with a 55 idle jet instead of the 50 I have now? I don’t have any, so I will have to order a set if you guys think this is the first step.

[Superhawk996]

I’d normally say increase the idle jet since you are turned out so far on the needles. Really you don’t want to be out 2 turns. That is a sign the jet isn’t big enough.

But . . .

It is also a sign of not having enough vacuum signal on the idle and transition ports which aligns to you inability to feed it throttle other than slowly leaning into the pedal.

So . . .

Since you have the 28 Venturis and don’t have bigger idle jets - put the 28 Venturis in

It may very well solve your problem

At a minimum it will give you information and a data point regarding how the larger Venturis are affecting your part throttle transition and whether it is a vacuum signal problem, a jet problem, or perhaps a little of each.