After several hours of jet swapping and test runs I have ended up with this setting for my 48 IDA :
Main venturi 40mm
Third progression hole drilled
Idel jet 65
Idle screw 1 turn out
Idle holder 100 ( the 60 holder was too rich at cruising speeds at 2000 rpm )
Main jet 150 ( with 135 it would lean out at WOT in 4th gear at 6000rpm)
Air Corrector 120 (could go smaller but have only 7x 115 air jets)
Emulsion tube very similar to F14 (was getting lean on high rpm with F19)
Pump bypass 00 (would bog down with a .50 when stepping on the gas suddenly).
As you see, if you change one settting it affects some other, so you have to combine until you get it right.
The lambda sensor has been of great value and would have made this tuning impossible without it.
I think I have the Webers pretty well set up now. Some fine adjustment is probably still possible. I will make myself a set of 42mm venturi and see if the engine is still as responsive.
The engine now revs smoothly from idle to the limiter, and when stepping hard on the gas from say 3000 rpm in 3rd it spinns the tires.
So the 37mm venturi is probably very good for a 289 or other SB as per this link
http://www.gt40s.com/forum/tech-engi...=wEBER+JETTING
but not the best choice for a BB 427.
In my case the running very rich with the popular Weber setting has ruined my rings and the car is up on the lift now to get new rings and god knows if not something else too.
Hope this has been of some help to Weber users with BB Fords.
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