layourman (2/23/2010)
Now can anybody tell me on the tbird holley where is the date code? is it a 3 number set and how do you read them, (not asking alot)The date code on the ’57 Holley is found on the front of the choke air horn and will be a 3 digit number. First number is the year, second number is the month, and third number is the week. November and December designations use A & B respectively instead of numbers. Ie. ‘6A5’ would be 1956, November, & fifth week while ‘711’ would be 1957, January, & first week. These two datecode numbers came off of a pair of 1273 carbs I have.
Per the ’57 Ford parts catalogue:
The Holley 4V carbs were factory installed on 1957 Ford cars and Thunderbirds with the 312. The Ford number on the carb is ECZ-AC, ECZ-AD, ECZ-V, or ECZ-Y.
The Ford (Autolite style) 4V carbs were on 1957 Ford cars with the 312. The Ford number on the carb is ECZ-U or ECZ-Z.
The Carter 4V carbs were on 1957 Ford cars with the 312. The Ford number on the carb is ECZ-AA.
My own experience mirrors that of John and the others in that the 1957 Thunderbirds with a single four carb came only with the Holley carb but any of the three 4V carbs that were available could be on the the 312 equipped Ford cars. Recent dyno testing of the three original carbs restored back to factory specs while on a stock intake shows the Ford carb to have a slight edge over the Holley while the Carter 4V carb lagged significantly behind the other two. Issue #97 of the YBM will have an article that goes into detail on sixteen different 4V carbs that were run on a stock intake on the 312 dyno mule with stock G heads.