[Eljaro]

Here I am answering myself again!
I want you Weber users know how my tuning is going on.
Remember that I am using Lamda sensor welded into the exhaust and I am checking on it all the time.
Took the Cobra out today(sunshine and beautiful weather here) to test the new 40mm venturis. I just bored out the 37mm ones on the lathe.

WOW! What a difference in top end power.
Perfect transition also, no strange spots anywhere, revs up to the limiter like a rocket.
I always considered that the basic Weber jettings which are mentioned in other threads was for a 289 cid engine and a 427 should needs more breathing.
I have the 48IDA Webers now jetted with:
60 Idle
60 idle holders (definitely the best option)
F19 similar tubes (F11 did worse, didn't try F5 )
145 main jet (140 might be better, have to try tomorrow)
130 air corrector (still going slightly leaner at top end , may try 125 or less).
The 55 pump bypass will have to come out for the closed one (ping and hesitation when going full on the throttle from slow speed ).

This setup was used today on a 700m stretch of 4 lane road with very light traffic, no cops and a bus stop where to park the car and make jet changes. Top speed reached 140mph before having to brake hard before the next roundabout.
The 37mm venturi may run on any engine and make everybody happy, but getting more out of the 427Fe with larger chokes without compromising drivebility is absolutely possible.