Earl,
Do yours have the long serial number pad or the short pad?
Per Dan Cases comparison with the Porsche 46IDA (diecast) application. The 46IDA (-2,-3) Series was a replacement for the 46IDM (sadcast) that was discontinued for the 4-cam four cylinder engine applications which ended in 1964. The IDA Series was a direct teplacement for the IDM Series that were made obsolete by Weber. I would suspect that the 46IDA evolution paralleled the 48IDA Series carburetors.
Based on my collection of factory documents and manuals printed in Italy and America I believe that the 48 IDA, 48 IDA1, 46 IDA2, and 46 IDA3 were all released to Ford/Shelby/Porsche at the same time roughly late March or early April 1964.
48 IDA and 48 IDA1 models (with 42 mm chokes) differed only by one part, two different styles of throttle lever.
46 IDA2 and 46 IDA3 models differed only by one part, two different styles of throttle lever in the manner 48 IDAs and 48 IDA1s differ.
The earliest documentation of any kind I have come across for the 48 IDA4 model is in hand written personal correspondence post marked June 28, 1966 between Dean Moon and a potential customer. 48 IDA4 models were factory fit with 37 mm chokes. Mr. Moon’s information tells the potential customer that 48 IDA4 models are for engines too small for 48 IDA1 models. {February 1967, GEON, WOODBURY NEW YORK, "48IDA4 COBRA (SHELBY)", no pricing available, under price is “P.O.A.”, printed in U.S.A. This is the earliest catalog mention and only printed information during the 1960s related to the “48 IDA4” that I have located to date. This is a Geon publication and not one from Weber, Ford, or Shelby.}
I have collected information on over three hundred carburetors between Serial Number 2 and Serial Number 5021. Ford and Shelby American wise I have not come across units associated with a new car build past the early 12xx serial number range SO FAR. One large caveat, at least three different and perhaps a fourth company have made counterfeit carburetors since at least 1971. Some of hard to detect as fakes and some are not. Just knowing a unit’s model and serial number is not enough information to have an idea if the assembly is genuine or bogus.
Printed Or Hand Written Period Factory Information Found To Date
1963 ~~~~~~~~~~
September 7, 1963, “WEBER DIS. No 20484 Misure d’ingombro carburatore tipo 48 IDA” dimensional and assembly drawings for the 48 IDA 2C design carburetor
October 2, 1963, parallel style COBRA lettered intake drawing (all carburetors face one way) Shelby American Inc. intake drawing (Remington/Moore) [It is believed that CSX2431 was the first car to get one of these new intakes in mid 1964 AFTER Ken Miles started using the car as a test and development mule. The day one pictures SA took of the car show the standard FIA approved type opposed system.]
1964 ~~~~~~~~~~
June 1, 1964, S.p.A. Edorado Weber, 46 IDA - 48 IDA models, “ENGINES WITH V CYLINDERS”, “NORMAL OPERATION”, printed in Italy
June 15, 1964, S.p.A. Edorado Weber, 48 IDA - 48 IDA 1, 46 IDA 2 - IDA3, “WEBER MASTERCATALOGUE – SPARE PARTS”, implies that 46 mm models are for “PORSCHE 904 G.T.” and that 48 mm models are for “8/C – V engines”, printed in Italy
1964 onward (original company and period) Edorado Weber 48 mm IDA-2C (two choke) master rebuild kits and overhaul gasket kits only list “48 IDA – IDA1” carburetor models. The sealing tapes on master kit containers reads “92.1050.05 – Type 48 IDA-IDA 1 FORD Cobra LOTUS”. (I take these terms to mean, FORD = GT40, Cobra = Cobra, LOTUS = Lotus 30 that were powered by 289 “Cobra” engines.)