I WENT FOR THE HOLLEY REFURBISHED 600CFM ON MY 292 WITH 574V DEVIDED PLENUMS.ECZ HEADS CONVERTED TO 57312 INTAK VAVES. 3.71REAR AXEL 4SPEED  4TH OD. RUNS GREAT. IN MY 1949 MERC 1/2TON. THE GUY FROM HOLLEY SEAD MOST OF THE RETURNS HAD NO ISUES,INSTALLER LEARNED AFTER THEY GOT #2 ON WARANTEE

I bought a new Holley 465 for the Tbird a while back. I think they are not available new anymore.

Meteor, what camshaft did you install?

The best carburetor under the sun is only half of the equation, in my experience ignition is the bellwether ingredient. I have Taylor wires, Mallory E-Spark pointless conversion, new Mallory tach drive distributor, MSD 6A ignition box with recommended coil and a Summit 600 CFM carburetor sitting on a stock B intake. It runs like a cat in a thunderstorm.

1955 312 T-Bird Warwick, NY

6 VOLTS/POS. GRD. NW INDIANA

Peeeot:  As already mentioned, I'm not sure why you want to make a change?  However, while that Ford Autolite you have was not as common in '57 as the Holley carbs, it was available. From what I've garnered from info in Y-Blk magazine & elsewhere, it's likely to give you the best fuel mileage, partly due to having  "annular" discharge nozzles above the venturies. While not more powerful, in a back to back dyno test printed in the the magazine, it was "30 percent" better than one of the other carbs in fuel consumption..         


Paul

The “why” is because I like to tinker and I enjoy carburetors.

I have found that most articles addressing how performance is affected by changes made to any particular aspect of an engine do so exclusively at wide open throttle and typically on a dynamometer. I have never seen a carefully planned and executed “apples to apples” fuel economy comparison between different carburetors, ignition systems, transmissions, etc. and think it would be fun to try to do such a comparison myself. Perhaps I’ll end up right where I started, but I’ll have learned something along the way!

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

If your objective is to test every carb, ignition, transmission, etc. combo/w goal of determining which combo will provide the best fuel economy, it will be a full-time job, requiring lots of parts. Conducting such tests in a controlled setting (on a dyno), probably won't be conclusive. In the real world, you have to consider traffic conditions, weather conditions (wind/temperature), road conditions, elevation, and so on. My guess would be that a 272/w stock heads, a bit more compression (zero-decking/milling), metric rings (reduced friction), Holley 390 cfm 4-bbl. carb, 1 1/2" headers, stock cam, no power steering or A/C, manual transmission/w OD, and rear axle ratio around 3.00 will be hard to beat as far as MPG is concerned. 

CASCO delivered one today.

6 VOLTS/POS. GRD. NW INDIANA