Great thread and info, folks,
I'm compiling chronological spreadsheet of Weber DCO Tipos for future dissemination and have some info to add for FIA regs.
This Weber spec sheet variety from 1960-1973
http://www.iw1axr.eu/Manuali_off/WEB...20-%201973.pdf
has all DCO3s discontinued by May 1960, including those for Coventry Climax 1.5, which may be significant.
It also has 42DCOE3s for Maserati 3500GT discontinued by that date, replaced by 42DCOE6/8. First few 3500s built late 1957, none yet seen with DCO3s, but many early cars went back to factory.
40DCOE2s used on Alfa Veloces etc., awaiting changeover date from DCO3s, but mid 1959 seems likely.
45DCOE4s original spec for Aston DB4GT, introduced Sept 1959.
38DCOE1s used by Stanguellini, maybe others, on Fiat 1100 lumps for early Formula Junior single seaters from late 1958 for 1959 season. No FJs yet seen with DCO3s, but Stanguellini, Osca, ASA, Moretti, Siata, etc. used smaller DCO3s previously.
Dagrada also used DCOEs on Lancia V4 Appia lump in FJ -- not sure of start date, but has to be the most ingenious head conversion/Weber fitment ever invented -- and sounds awesome!
Are the FIA's objections to the use of Webers per se in pre-1960 racers, or of the substitution of DCOEs instead of unobtainable OE DCO3s?
Hope this all helps. Any other dating info gratefully received.
Rob