Tunnel Port heads and inductions only came into use near the end of Cobra production and had nothing to do with the Cobra. Bruce, I don't dispute that your monster cubic inch modern fuel injected engine would outdo my old technology, my interest is just more into the nostalgia, as the big weber inductions were a part of the development and history of the big block car and were optional race pieces for them. Webers were integral to the heart and soul of Ken Miles and Shelby American and that philosophy was being carried over from the small block to the big block cars, just ultimately not fully exploited, as with many other aspects of the 427 car. The big block Supercoupe is probably the best example of the pinnacle of Cobra withdevelopment that didn't get its fair opportunity in "combat", but that does not take away from its special place in the history of these cars.
Here is how the first big block car prototype engine came into SA from Ford by June of '64, equipped with an 850 Holley:
http://www.clubcobra.com/photopost/s...=47517&cat=500 This was the aluminum 390 with aluminum high riser heads that were cast special just for Shelby.
Shelby American still had substantial control over its racing development activities at that point and, like the small block race engines, did some of their own development on the big block. It is believed the two styles of high riser weber intakes were specially made for the Cobra during this development period (the inline carb one to maximize hood clearance under the crown of the Cobra hood). Guys like ex Ford employee Ernie McCune (sp?) involved with racing activities said a batch of the 58mm webers were specially made for Shelby American in early '64 to use on the Cobra, which they installed on this prototype engine in place of the Holley:
http://www.clubcobra.com/photopost/s...=47518&cat=500
This configuration notably outperformed the Holley, making reportedly over 500hp from only 390 cubic inches and tiny 390 sized valves. SA decided this was the optimal setup to run and went on to install this engine into the big block configured coupe (
http://www.clubcobra.com/photopost/s...=47492&cat=500) for an assault on Lemans in '64 - it was to be Shelby's "secret weapon". The car was damaged in a transporter accident on the way to Lemans and returned to the shop, but SA employees were in awe of its potential. This engine, with webers, was later run in the flip top car.
Documentation from Ray Geddes to SA around August of '64 specified several big block race cars that were to receive these engines for the '65 season. Another Geddes memo dated about October of '64 (I haven't looked at these in some time) specified cast iron 427 blocks to be used in the race cars instead of aluminum, although Shelby would have probably still used the two aluminum ones he already had, as evidenced by the subsequent use of one in the flip top car in December at Nassau. Even after Ford changed the block specification from aluminum to cast iron, the 58mm webers were still planned on being used, as they were included in the FIA homologation paperwork at the end of '64/early '65. Early documentation just specified aluminum for the cylinder head material, leaving the option open of using MR or HR castings (the 58mm intake manifolds were only made for the HR head), whereas later in '65 just the MR P/N was specifically called out.
By the end of '64, Ford had taken much more control of SA's activities and all emphasis and key employees were diverted to the GT40 effort. With all the emphasis taken off the Cobra, the big block Supercoupe was starting to experience delays and problems. The writing was on the wall and finally when Shelby American was refused homologation around March or April of '65, the big block Cobra became a still born race car and many of the trick things the key SA race team members developed, like the big webers and big block coupes never had their chance at ultimate glory.
From the point Ford started having major influence over SA's operations in '65, SA employees became notably limited in what they could do with many of the engines. Race engines came in pre-assembled from Ford Engine and Foundry and SA employees in large part were not allowed to take them apart, including changing inductions. Bean counters and other Ford influence made the big block Cobras go out the door with more cost oversight than how SA had previously approached the small block cars (just look at the SA invoices....big block cars almost always had no options vs small block cars were often loaded with different equipment), also driven by Shelby's attention shifted to the GT effort. CSX3005 (a comp car) was a good example of this changing philosophy - it was being "optimized" by the factory, but when it came time to deciding who was paying, the car ended up being disassembled and the parts sold off or used in various ways. Earlier on, SA would likely have footed the bill just to get the visibility and promote Cobra racing success - now they figured they achieved what they wanted with the car.
The coil spring Cobras, including the comp cars, ended up being delivered in more basic form, with SA not as receptive to do as many add ons at the factory as they did with leaf spring cars. This was dictated from Ford's Ray Geddes mandate that the 427 just be a "customer car". Many things needed to optimize the cars for racing were left up to the owner to incorporate, with Shelby American offering most of the necessary items (including the webers) over the counter - although in many instances such specialty items were in short supply and SA would only freely "open up" availability to prominent racers. The 427 Cobra was being sold under a different mandate than modern supercars such as the Z06, etc. On the street, the Cobra in it's day was so fast relative to everything else, that SA employees had commented in discussions about parts outfitting that all the bells and whistles were not necessary and if someone wanted such trick parts they were available separately.
So, I hope this provides a fair picture of how special hardware like the webers fit in with the big block cars.
More weber comparative and sizing data to follow when time permits.