My reasons for doing this stem from improved long term reliability, the elegantly simple DIY repair requiring no special tools with the improvement in power, throttle response and sheer personality from retrofitting the classic Ferrari OEM induction. This is not an original idea of mine, as the Porsche 911 community has been retrofitting Webers to Bosch K-jet cars (2.7 and 3.0 liter) with great success for years.
The key parts are four beautifully cast manifolds that fit the 3.0qv/328 head from Frank Capo of Modena Engineering in Australia. I know Carobu do business with him, but I found my manifolds at Blackhorse. Be sure to trim and match the stock gaskets to the intake
ports. Only a small vacuum tap was needed for the ventilation control system, as the Mondialís ABS brakes do not require a vacuum line in this application. Everything actually just bolts up like it was original. There are now manifolds also available out of Germany for Webers on qv/3.2 heads, with vacuum taps for the earlier power brakes.
Four new commonly available Weber 40DCNF-12s were purchased as well as the large Facet fuel pump used as a replacement for the Ferrari Corona unit. I will make a long development story short by saying one right answer is setting up the Webers with 34mm venturis, 135 main jets, F24 emulsion tubes, 190 air correctors and 53 idles. It of course depends as well on what cams, air filter and exhaust you have. Stock K-jet cams were used, as well as a stock early 308 airbox, which bolted right up. The linkage, was fabricated with parts from Pierce Manifolds and original 308 carb arms. the side scoop was cut and modified to allow a cool air duct to the airbox.
Best chassis dyno numbers obtained was about 242 rear wheel hp, which with common 17% loss correction places it at about 290 flywheel hp (Factory rating of 260). The sound of the 4 valve engine with Webers is simply not comparable to the original Bosch K-jet injected version. It is a magnificent awe-inspiring sound.
This is a very easy retrofit to do for an amateur, requires no special tools, and really adds to my enjoyment of the car.
Hope this is entertaining for some.