How To Identify Mustang Carburetors
Quick Facts From Pony Carburetors To Help You Find The Right Carb For Your Vintage Mustang
Ford has been installing electronic fuel injection on Mustangs for the past 26 years. Carbureted Mustangs encompass the rest of the marque's 45-year history - some 21 years of production - which means there were a lot of Mustangs built with old-fashioned carbureted induction. The last Mustang with a carburetor was the '85 Mustang GT, which was fitted with a "no-tamper" Holley 4180.
When the Mustang was introduced on April 17, 1964, there weren't many carburetor types. In fact, all were Autolites. What was used depended upon engine type, automatic versus manual transmission, and where the vehicle was delivered. There wouldn't be a Holley carburetor until 1967 when the popular performance carb saw duty on the 390 High Performance for a short time.
We've known Jon Enyeart at Pony Carburetors for at least two decades. When it comes to classic and late-model carburetor identification and application, Jon's the "go-to" guy for specific information. The news from Jon about Mustang carburetors is generally good, but it isn't always positive because good cores aren't always available. If you have an '80 Mustang with a 255ci small-block and the California emissions-mandatory Motorcraft VV (Variable Venturi) carburetor, you will learn from Jon that these rare emissions carburetors are hard to find and not cheap when you do find them. You could say the same thing about a 780cfm Holley 4160 for the Boss 302 or an Autolite 4100 for a 289 Hi-Po - hard to find and expensive.
If you have a mainstream Mustang with a dime-a-dozen Autolite 2100 two-barrel, the news is generally good-and it won't cost you a fortune.
The Autolite 1100 one-barrel carburetor was offered on the 170 and 200ci sixes from '63-'69. There were three venturi sizes - 1.00-, 1.10-, and 1.20-inches. Mustangs had either 1.10- or 1.20-inch depending on model year and configuration. Basic bore size was 17/16-inches. Understanding how the 1100 works takes some imagination, but it isn't much different than any other one-barrel carburetor of the era. What makes it different is how it interacts with the ignition system. The '63-'67 1100 carburetor has a spark control valve (identical to a Holley/Autolite/Motorcraft power valve) which was not used on '66-'67 California emissions or '68-'69 50-state 1100 carburetors. The spark control valve was used in conjunction with the Autolite single-point Load-O-Matic distributor. This distributor did not have a mechanical advance; instead it used venturi vacuum (throttled vacuum) at higher engine rpm.
According to Jon Enyeart, the Autolite 1100 experienced significant changes that adversely affected performance in the late 1960s. In 1968, Ford downsized to a 1.10-inch venturi and eliminated the spark control valve to help reduce emissions. Instead of a vacuum advance, six-cylinder distributors were purely mechanical advance, which hurt performance.
If your six-cylinder Mustang struggles with hesitation, stumbling, and hot starting problems, you're not alone because this is an inherent design flaw in the 1100 carburetor. Pony Carburetors has managed to engineer this problem out of its rebuilds. However, other performance issues remain. For one thing, the 170 and 200ci sixes have an integral log-style intake manifold and cylinder head, making it impossible to achieve uniform fuel distribution to all six cylinders. Cylinders 1 and 6 don't get adequate fuel distribution, resulting in unpredictable idle and stumble on acceleration.
The 1100 carburetor has the same kind of automatic choke found on 2100/4100 carburetors-an exhaust manifold-heated thermostatic coil with vacuum-induced choke unloader to reduce cold-start emissions and spark plug fouling. Six-cylinder Mustangs were never produced with a manual choke.
Autolite 1100 carburetor identification is done by examining the base plate and searching for numbers. Look for the Ford part number for initial identification. Prior to '67, 1100 carburetors had one accelerator pump diaphragm. From '67-'69, there were two, with the second diaphragm acting as an anti-stall dashpot instead of an accelerator pump on automatic transmission models. If you see a spark control valve (looks like a power valve), you've found a pre-'68 1100 carburetor. The best way to identify size is venturi inside diameter - 1.00-, 1.10-, or 1.20-inches. The Mustang's 200ci six runs best with 1.10- or 1.20-inches. Ideally, you will go with the 1.20-inch for optimum performance.
The all-new 1100 Vaporizer carburetor from Pony Carburetors is not a rebuild. Instead, it's a totally new carburetor with all of the woes engineered out for optimum performance. Pony Carburetors has taken the annular discharge design found in 2100/4100 carburetors and incorporated it into the 1100 for better performance. It improves fuel atomization for a smooth transition from idle to power circuit, inducing better throttle response. It took a lot of research and development to get the Vaporizer to market, which means you're getting a well-engineered carburetor that employs the best technology available from a vintage design carburetor. Each Vaporizer is run-tested in the Pony Carburetors' engineering lab before packaging.
Like all Pony Carburetors' products, each new 1100 Vaporizer is shipped with detailed instructions plus a filter and gasket for installation. When you consider how challenging it is to find a serviceable 1100 carburetor core, plus the cost of rebuilding, the Vaporizer is an excellent value at $429.50 plus shipping.
Ford introduced the Autolite 2100 and 4100 carburetors on the '57 Ford Y-Block V-8. Ironically, that same year Holley came out with its own line of performance carburetors with removable fuel bowls, metering blocks, and similar design nuances to the Ford/Autolite 2V and 4V carburetors. We've never been able to determine which came first - the Autolite or the Holley. However, both have proven legendary in terms of performance and reliability over more than 50 years of use.
The 2100 and 4100 were direct replacements for Holley 4000 "Teapot" carburetors used on the Y-Block Fords prior to 1957. Holley 4000s were also known as "Haystacks," "Coffee Grinders," and "Fireboxes" due to their design and nasty habit of catching fire. Suffice it to say the 4000 needed to go when a new generation of carburetors from Ford and Holley came along.
What makes the 2100 and 4100 significant to Ford history is engineering advances at the time. These are the first Ford carburetors to have annular discharge booster venturis, which smoothed out the transition from idle to power as the throttle was opened to eliminate hesitation. Although we will get arguments from Holley fans, the 2100 and 4100 can easily be called the most reliable factory carburetors ever made. They tended to be limited by venturi and throttle bore size (CFM), which made Holley the performance champ. The main difference in these carburetors is size. The 2100 came in sizes ranging from 190 to over 400cfm, with the 4100 ranging from 480 to 605cfm. The 2100 two-barrel is nothing more than a 4100 without secondaries. This means there's a lot of interchangeability between the two types.
The 2100 carburetor consists of a main body and air horn, throttle plates and shaft, accelerator pump, and automatic choke assembly. Each throttle bore, or barrel, contains a main and booster venturi, main fuel discharge, accelerator pump discharge nozzle, and throttle plates to control air/fuel flow. Fuel comes from one bowl where fuel is regulated by a float and needle valve. As fuel is atomized and burned, the float drops, unseating the needle valve to allow fuel to flow into the bowl. Floats are made of either brass or synthetic foam. Main metering jets screwed into the body regulate flow to booster venturis during power mode. They have no effect on idle mixture. Idle mixture screws (needles) regulate air/fuel mixture when the throttles are closed.
The 2100's accelerator pump system works off a cam located on the throttle shaft. As throttles are opened, the cam moves a lever, which leans on the accelerator pump diaphragm, injecting fuel into the throttle bores. This eliminates hesitation, providing a seamless transition from idle to power. The accelerator pump chamber has a check valve (either rubber or a steel ball) which allows fuel flow in from the fuel bowl and out via throttle bore nozzles.
A 2100's choke system works much like the 1100. A thermostatic, bimetallic coil spring gets its heat from a hot exhaust manifold. Heat is drawn via intake manifold vacuum to a coil spring, which, as it warms, expands and pulls the choke open. A choke unloader helps pull the choke open via intake manifold vacuum to reduce cold start emissions. A fast idle cam incorporated into the choke bumps the idle higher during choke operation for faster warm up. There is a fast idle adjustment as well.
The 2100 two-barrel carburetor ultimately evolved into the 2150 with a more sophisticated choke unloader, which came along in the early 1970s. This carburetor was in production until the mid-1980s.
It wasn't until the '67 model year that Mustang got its first factory-installed Holley carburetor. Yep, we know the '65-'66 Shelby Mustangs were fitted with a 715-cfm Holley 4160 with LeMans float bowls, however they were installed at Shelby American. Jon Enyeart tells us there are two basic types of Holley carburetors that apply to Mustangs-the 4150 and 4160. There is a third one you see from time to time-the 1850, based closely on the 4160-as a standard garden-variety 400-600-cfm Holley replacement carburetor. The 4160 has only a primary metering block whereas the 4150 has both primary and secondary metering blocks. The 4160 utilizes a secondary metering plate, which takes the place of a metering block. It can be replaced with a metering block to create a 4150.
The Holley 4150 was factory installed on a Mustang for the first time in 1967 atop the 390 High Performance. That same year, Shelby American would top the 428 with a pair of 4160s. The 4150 carburetor was fitted with "Cathedral" center-pivot fuel bowls. Those 4160 carburetors got side-pivot fuel bowls.
Holley carburetors are identified differently than Autolites. If it's an aftermarket Holley, it will have only a List number and Julian three-digit date code and year on the air horn. If it's a Ford/Holley carburetor, it will have both List and a Ford part number/date code on the air horn. If you've found a Shelby/Holley carburetor, you will see the List number and a three-digit date code without the Ford part number.
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.
Although the majority of Quadrajets were manufactured for GM vehicles, a handful went to Ford, and they were unique to the 429 and 429 Cobra Jet. You can't install just any Quadrajet on a Ford because they have a different throttle linkage and kick-down lever. Ford Quadrajets have a straight-in fuel line design intended for Autolite/Motorcraft screw-in fuel filters, unlike their GM counterparts. Rochester didn't stamp a Ford part number into Ford Quadrajets. Only a tag was used, which makes these carburetors like a needle in a haystack unless you know what you're searching for. Look for a GM number in the casting - 7040285, 7040286, 7040287, or 7040288. Anything outside these numbers is not a Ford application, according to Pony Carburetors.
Ford Carburetor ID Guide
When you're as passionate about carburetors as Jon Enyeart, you learn everything you can about them. Jon has been in the carburetor business for 30 years and messed with them even before that. His Ford Carburetor Guide is an exceptional tool if you're searching for the right Mustang carburetor. You can get a copy by calling Pony Carburetors or through their website.
Carter YF & RBS
Although the Autolite 1100 gets a lot of attention for its extensive use on Ford sixes, it wasn't the only six-cylinder carburetor. Carter is a name we associate with Chrysler products of the era, but Ford also used its share of Carter carburetors. The Carter YF first saw use on California emissions 170 and 200ci sixes in 1967. In '68-'69, only 170 and 240ci sixes got the Carter YF, which means you will never see one on a Mustang. When the Autolite 1100 was phased out in 1970, Mustangs got the Carter YF on 200ci sixes. The Carter YF is a little squat-box one-barrel carburetor with metering rod function like the larger Carters. It is a better carburetor than the Autolite 1100, although Jon Enyeart tells us the YF suffers from a poor accelerator pump design, which gets fixed during a Pony Carburetors' restoration.
The YF carburetor does not have a Ford part number on the body. Your best shot is the carburetor tag if it remains. There is a Carter number stamped into the body, which helps. You're looking for a Carter YF #6051. YFs came in 150, 170, 187, and 200-cfm sizes.
The Carter RBS was used only on the Mustang's largest six-cylinder engine, the 250ci six, from '70-'73. Like the Carter YF it replaced, the RBS is a metering rod design actuated by intake manifold vacuum. And like the YF, it also struggles with poor accelerator pump function. A Carter number #2191 is cast into the RBS body.
In 1972, Carter began producing these carburetors with the words "Mfd. By Carter for Motorcraft," which makes them easy to identify. Only one size-215 cfm-was produced.