How To Identify Mustang Carburetors
Quick Facts From Pony Carburetors To Help You Find The Right Carb For Your Vintage Mustang
You might be inclined to ask why Ford didn't develop its own high-performance Autolite carburetors. In some instances, it did, such as the Autolite in-line four (also known as the Cross Boss) and the 4100s used on the 289 High Performance. From an economic standpoint, it made more sense to give Holley the opportunity to develop high-performance Ford carburetors instead. Ford kept Holley busy between '67-'71, developing performance carburetors for FE-series 390 and 428 big-blocks plus Boss 302 and Boss 429. The '71 429 Super Cobra Jet engine would be Holley's last hurrah until '83 when it would return on the Mustang GT as the 4180 for three short years.
Understanding Date Codes
Date codes are found on the carburetor air horn. Expect to see three lines stamped in factory installed and service replacement Holley carburetors-Ford part number, Holley List number, and the date code. See the Ford Carburetor Guide from Pony Carburetors for more details.
If you've found an aftermarket Holley carburetor, expect to see two lines of information stamped in the air horn - Holley's traditional List number and a date code based on the Julian calendar with days 001 through 365 plus year of manufacture. Look for this information in the very informative Ford Carburetor Guide as well.
Autolite Motorcraft 4300
Many throw tomatoes at this carburetor, so it calls for understanding if you're going to get along with it. Although we like the 4100 shoebox carburetor, it was not emissions-friendly by federal standards. With ever-increasing emissions standards coming in the late 1960s, Ford had to develop the 4300 almost overnight. It is radically different than the 4100 it replaced. For one thing, the 4300 was not an across-the-board replacement for all four-barrel carburetors. Some engines, including most big-blocks, were still fitted with the 4100 and Holley 4150s through 1972. The 4300 went through its share of teething problems early on and never managed to shed that reputation. Is it a better carburetor than the 4100? Depends on who you ask. As a rule, the 4300 has always been a disappointing emissions carburetor with more than its share of performance tuning issues.
Early 4300 carburetors were small - 441cfm - which was adequate for the 289 yet inadequate for 390s. For '68, Ford came out with a 600cfm 4300 for fuel-thirsty big-blocks. The early ('67-'68) 4300s can be identified by a fat curb idle screw in back of the body. The 4300 continued to evolve through the early 1970s when Ford replaced it with the 4350, virtually the same carburetor, 600cfm in size, found on the 351C, 429, and 460 engines. Challenging to find is the Autolite 4300D, a 715cfm spread-bore four-barrel that was used on the Boss 351, 351C High Output, and 351C Cobra Jet. More details on the 4300 and 4350 can be found in the Ford Carburetor Guide from Pony Carburetors.
Ford purists cringe whenever this subject comes up, but Ford did indeed install the GM Rochester Quadrajet on the 429 V-8 in '70-'71. General Motors introduced the Quadrajet in 1965, which made these vehicles legendary for their throaty bellow whenever the accelerator was mashed. The Quadrajet was the auto industry's first spread-bore design and, properly tuned, it is an excellent carburetor. "Spread Bore" means huge secondary bores with small primaries for improved fuel economy. The Quadrajet has an air valve secondary system just like the 4300 and 4300D. It is also the same 715cfm size as a 4300D.