Weber 44 idf flat spot Options

[tornik550]

So I recently purchased new weber 44 idf's. They didn't work out well so I went back to an old set of weber 44 idf's that I had. I thoroughly cleaned the carbs, sprayed carb cleaner through all jets, tubes, etc. I have also balanced the linkage. Set the floats, etc.

The car starts well. Idle's well. When I drive the car I get a major flat spot between 1500 and 3000 rpm's. Below and above the car accelerates normally.

What changes should I make?

My current setup for my 2258 (dual webers, big cam)
-idle 55
-main 160
-et F11
-ac 200
-vents 36

Are there other issues that can cause this type of problem (timing,etc?)

[ChrisFoley]

If you back off the nuts on the accel pump rods and completely remove the main jet assemblies you can drive around to see what the mixture is on the low speed progression circuit without any other influences.
The engine probably won't run over 3000rpm, maybe even lower.
Size the idle jets to give you 16-17:1 driving around at very light throttle.
Then adjust the idle A/F with the mixture screws.
You should be able to get around 14:1 at 850-900 rpm.

Reinstall the jet stacks and size the Main jets for 12.8:1 at wide open throttle above 4K rpm.
Then increase the air corrector jet size to get rid of leanness in the midrange.
It may be necessary to increase the mains one more size, depending on how big you had to go with the A/C jets.
The last step is to screw the accel rod nuts back in to eliminate any lean hesitation when you step on the throttle.

If you can't get rid of the lean transition switch to the next smaller main venturi size.