The small-block Ford’s 39-year production life included a broad array of induction systems ranging from the humble 2-barrel carburetor, to high-performance Holleys, to throttle body and port electronic fuel injection systems. What your small-block Ford calls for depends on when it was produced and what type of Ford, Mercury, or Lincoln it powers.
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The small-block Ford’s production life (1962–2001) consisted of primarily Autolite and Motorcraft carburetors with the exception of the Holley 4150 used on Shelby Mustangs and the Boss 302. Ford opted for the Autolite and Motorcraft atomizers because they were extremely reliable and easy to maintain.
Ford 221, 260, 289, 302, 351W, and 351C 2-barrel small-block engines were factory fitted with dual- plane iron intake manifolds and the Autolite 2100 2-barrel carburetor. Ford enthusiasts like the 2100 for its simplicity and ease of service. The 2100 lasts longer than any other carburetor between overhauls because it is so simple. Ford’s 2100 carburetor was first introduced in 1957 and remained in production well into the 1980s as the 2150.
This is the 4100 from a different angle, revealing the heat-operated automatic choke system with fast-idle cam and adjustment. Intake manifold vacuum draws exhaust heat through a tube from the exhaust manifold, which acts on the thermostatic spring and choke plate. Ideally, you hand tune the automatic choke for minimal choke and get a good clean warmup.
Although the 4100 “shoebox” carburetor didn’t set any land speed records, it is easily the most reliable atomizer ever made. The 4100 offers the same size benefits as a comparable Holley 1850/4150/4160 in sizes ranging from 480 to 600 cfm. You can run the 4100 on an aftermarket or Cobra high-rise manifold and achieve the same kind of performance you’d get from a comparable Holley 1850/4150/4160.
FYI, Holley carburetors make good drop-in replacements for the 2100 and 4100 without losing reliability. The Holley 1850 and 4160 are easy to maintain and service. In fact, Classic Tube makes a custom fuel line for Holley carburetors installed on small-block Fords.
Induction systems for the small-block Ford are easy to understand: simple dual-plane, cast-iron manifolds topped with one basic type of carburetor. Carburetor identification is straightforward based on throttle bore size. For example, a big-block Autolite 2100 has larger throttle bores than those used on a small-block. A big-block 2100’s throttle plates do not open to capacity on top of a small-block carburetor spacer. Likewise, a small-block 2100 stifles a big-block. Carburetor type/size is determined by venturi diameter, which is cast into the driver’s side of the body near the accelerator pump. You can expect to see .98, 1.01, 1.02, 1.14, and 1.23, which is the venturi diameter in inches.
Although the 221 was in production for a short time, 1962– 1963, it included eight 2100 carburetor types with the smallest having .98-inch-diameter venturis at 190 cfm. The 260 and 289 were fitted with larger 1.01-inch venturis at 240 cfm or 1.02 inches at 245 cfm depending on application. Venturi size depended on transmission, vehicle application, and the original selling sales district.
California emissions carburetors were originally jetted differently than 49-state carbs. This was also true for high-elevation destinations such as Denver where jetting was leaner. For 1964, the 289 received larger venturis to improve power, 1.14 at 300 cfm. This improved low- and mid-range torque.
Carburetor identification tags weren’t used on 2100s and 4100s until 1965, which means all you have to go on is linkage style and venturi size, the latter being cast right into the main carburetor body.
The most significant 2100 changes came in 1964 with an improved accelerator pump, choke unloader, and National pipe threads at the fuel inlet. Even more changes came in 1966 with the deletion of brass fuel bowl vent tubes. In 1968, the fuel bowl received a controlled vent system to reduce evaporative emissions. In 1970, in an effort to reduce emissions, a choke unloader diaphragm was added to the air horn to improve cold-start performance.
The 289 High Performance V-8, introduced in 1963, was the first small-block Ford equipped with an Autolite 4100 carburetor; it originally came with an automatic choke and choke heat tube. The 289 High Performance V-8 received a manual choke in 1964 on its very hard-to-find 4100. When Mustang was introduced in the spring of 1964, Ford introduced the one-year-only 289-4V low-compression regular-fuel V-8 also with the 4100 carburetor with 1.08-inch venturis at 480 cfm. The Hi-Po received a larger 1.12 carburetor with 600 cfm at wide-open throttle.
The 4100 is as simple as the 2100 2-barrel and of a design nearly anyone can understand and service. The 4100 dates to 1957 when it was first installed on Ford’s legendary 312-ci Y-block V-8. In its 10-year production life, the 4100 was produced in four sizes according to the late Jon Enyeart of Pony Carburetors.
The most common size was 1.12 inches, cast in the main carburetor body. Small-block Fords were fitted with the 1.08-inch 480-cfm 4100, which yields the best low- to mid-range torque. The 1.12-inch-bore 4100 yields 600 cfm and is also a good fit for the 289/302. It can also be too much carburetor if not properly jetted and tuned. The 600-cfm 4100 works quite well when you have a 289/302 that’s up to the task with a hotter cam, larger heads, and a deep-breathing exhaust system.
As with the Holley 1850/4150/ 4160 carburetors, the 4100 has a diaphragm-style spring-loaded power valve designed to function off intake manifold vacuum and power demand. When additional power is needed, the power valve enriches the fuel mixture to meet the demand. The 4100’s accelerator pump is similar to the Holley’s as well with a diaphragm, spring, and check valve and amazingly simple function.
The 4100’s vacuum secondaries are activated by a vacuum servo at the back of the carburetor body connected to the secondary throttle plates via a plastic linkage. Punch the throttle and intense intake manifold vacuum draws the secondaries open. The key to proper function is for the manifold vacuum to overtake the servo spring pressure and open the secondary throttle plates. A safety system prevents unwanted wide-open secondaries and runaway engine RPM. The 4100 has removable annular discharge boost venturis in both primary and secondary throttle bores that can be removed
Deteriorating air quality in major U.S. cities began to attract the attention of environmentalists and Washington alike in the mid-1960s. Los Angeles, in particular, had dangerous air quality during hot summer months, posing a significant health risk. Ford set its sights on improving exhaust emissions levels. Some of it was voluntary. Some of it was mandated by Washington. The Auto-lite 4300 4-barrel carburetor was conceived to reduce emissions and improve performance. It did neither.
The Autolite/Motorcraft 4300 has never been an easy carburetor to service or tune. Ford was never able to get the 4300 and its successor, the 4350, to function properly. Its biggest shortcomings are hesitation and stumble, frustrating flat spots that drive people crazy.
Ford struggled with the 4300, with engineering changes every year to no avail. For one thing, the 4300 differed greatly from the shoebox 4100 it replaced.
If you’re frustrated with your 4300/4350, you’re not alone. That first year, 1967, only one size was offered, 441 cfm, not enough carburetor for the 390 but plenty for a 289.
For 1968, a larger 600-cfm 4300 was introduced for big-block applications only. The 441-cfm 4300 was dropped in 1970 because it made little sense to keep it in production.
In 1974, the 4300 was dropped in favor of the redesigned 4350, which was even worse than the 4300. The 4300 was an emissions-driven carburetor, which is why it struggles with performance and reliability issues.
In 1971, the Autolite 4300D spread-bore yielding 715 cfm was introduced for the Boss 351 and 351C-4V Cobra Jet engines only. What made the 4300D different was its spread-bore design, like the Carter Thermoquad, Rochester Quadrajet, and Holley Spread Bore.
It can be safely said that the 4300D is a very temperamental carburetor. For one thing, it is not inter-changeable with any other type of carburetor, which means carburetor and manifold are married and must be used together. Forget about using a Holley Spread Bore or Rochester Quadrajet because they do not fit. The key here is to learn how to live peacefully with this carburetor.
The 4300 and 4300D are identifiable by Ford part numbers cast into the body. If the identification tag has been lost you can find these numbers on the base at the driver’s side of the carburetor.
The greatest challenge with the 4300 is understanding how it works. Performance depends on proper calibration. The 4300 has mechanical secondaries like the Rochester Quadrajet’s but unlike the 4100, which has vacuum secondaries. As the throttle is stabbed and secondaries open, air valves on top should follow suit smoothly for a nice transition to full power. However, rarely does this occur as Ford envisioned.
Because the 4300 and 4300D have a tough time with air-valve timing, you can count on stumble and hesitation when the pedal is pressed. This is an engineering flaw in the 4300/4350-series carburetor that was never corrected in production. Hesitation and stumble are rooted in the extraordinarily lean mixtures that occur during the transition from idle to wide-open throttle.
Much of this problem centers around Ford’s jetting toward lean for reduced emissions in normal driving. Pony Carburetors has improved the 4300’s drivability problems; however, there are no guarantees. Proof comes when you install a 4300 or 4300D and see how it performs under actual driving conditions.
Motorcraft Variable Venturi
The Motorcraft Variable Venturi (VV) 2-barrel carburetor was an honest effort by Ford to clean up emissions. However, it has proven to be even more challenging than the 2100/2350-series carburetors. It doesn’t come cheap and it’s tricky to service. If you have to buy a rebuilt VV carburetor, you will pay around $1,000 at most auto parts stores if you can find one. If you attempt to rebuild one yourself, it’s an unknown whether you will be successful. A Ford Shop Manual is suggested along with a lot of patience.
The Motorcraft VV carburetor was introduced in 1977 on Ford’s 2.8L V-6 and the 302-ci small-block where it was used until 1982 on all California-delivered vehicles with this engine. The 255-ci small-block, which was available from 1980 to 1982, also received the VV carburetor. Although this carburetor has been a point of frustration for many because it is smog-law mandatory, it really is a marvel of engineering.
Venturis vary in size depending on throttle position and load. It has main metering rods and jets as on a Carter AFB/AVS carburetor. As the throttle is pressed, tapered metering rods allow more fuel to flow.
VV carburetors are identifiable by codes stamped into the upper body. When the ID tag is gone, codes stamped in the body casting are the only means of identification.
The Holley 4150 witnessed little factory use on small-block Fords, and only on Shelby Mustangs and Boss 302 Mustangs and Cougars. Shelby American used the limited-production centerpivot LeMans-bowl 715-cfm Holley 4150 on its GT350 Mustangs with 289 High Performance V-8s. These carburetors received a Ford part number during their first year in 1965, then received a Shelby part number through 1967.
Ford went with the 780-cfm Hol-ley 4150 atop the Boss 302 engine in 1969–1970. This carb was assigned a Ford part number along with a Holley List Number.
The part number, along with Holley’s List Number and date code, can be found on the air horn. The List Number is Holley’s number that falls in line with Ford’s engineering number. For example, if you’ve found a Holley carburetor from a Shelby GT350 with a LeMans bowl, the list number should be 3259-1. The Hol-ley List Number confirms it.
Shelby’s 4150 has a secondary metering block and flows 715 cfm at wide-open throttle. For 1968, Shelby GT350s received the 600-cfm 4150 Holley 4-barrel carburetor. Later in the model year, they were given the Autolite 4300 as a means of cutting costs and reducing emissions.
The rule with factory Holley carburetion is this: The 4150 has both primary and secondary metering blocks. The 4160 has only a primary metering block. Factory Hol-leys had vacuum secondaries. Ford never used a Holley with mechanical secondaries.
In 1983, Ford went back to 4-barrel carburetion for the first time in 10 years. With the Mustang GT and Capri RS came the Ford/Hol-ley 4180-C 4-barrel carburetor on top of 5.0L High Output V-8s with 4- and 5-speed manual transmissions.
Automatic versions received Central Fuel Injection (CFI). The 4180-C carburetor isn’t your typical Holley fourbore. It is a unique 600-cfm carburetor with antitamper technology. It is not computer controlled. Although the 4180-C is an anti-tamper carburetor, it can be modified for improved performance. Because Ford and Holley collectively did a good job on this carburetor, you really don’t have to change anything. You can add a secondary metering block, but you really don’t have to.
Like most Holley 4-barrel carburetors that came before the 4180-C, this carburetor has both a Holley List Number and a Ford part number. This is an easy carburetor to identify. For example, 1983 is identified by List 50223. Both 1984 and 1985 are List 50265.
Jetting with the 4180-C is also different than your conventional Holley carburetor. It has different jet size markings.
The performance improvements with the 4180-C are off-the-shelf Holley tried-and-proven techniques. Jet upsizing. Power valve swaps. Accelerator pump adjustment. Fuel filter removal. All these steps improve performance. Swapping the primary metering block is impossible, however, because it is specific to the 4180-C.
You can always shelve the 4180-C and install a conventional Holley 4150/4160. However, be advised that you’re wrestling with smog laws in many states. Your 5.0L High Output must be able to pass a visual smog check to be licensed in many states. Not all states have jumped on the environmental bandwagon, however, so be sure to check.
Several multi-carburetion packages were available from Ford for the small-block during the 1960s. The tri-power and two-four setups were available through Ford dealer parts departments as aftermarket performance accessories. Manifolds were produced by Buddy Bar in Los Angeles. Carburetion was always Holley. The Tri-power setups employed three aftfacing Holley 2300 series 2-barrel carburetors, with the center carburetors fitted with a choke for cold starting.
With three-deuce setups, two basic configurations were available from dealers. Center carburetors were C4GF-H (Holley List 2867) or C4AF-J (Holley List 2881). Outboard carburetors, front and rear, were C4GF-J (Holley List 2868) or C4AF-V (Holley List 2882).
Each of these carburetors flows 200 cfm at wide-open throttle for a total of 600 cfm.
Also available from Ford dealers was a dual-quad setup for small-blocks. First available in 1965 and 1966, the dual-quad intake was fitted with a pair of Holley 4160 carburetors. The primary carburetor was C6OA-A (Holley List 3360). The secondary carburetor was C6OA-B (Holley List 3361). Both carburetors’ combined flow was approximately 1,000 cfm at wide-open throttle.
Easily the most exotic production carburetor and induction package ever made was the short-lived Auto-lite In-Line 4-barrel. Two versions were produced: 850 and 1,425 cfm. The 850-cfm version (D0ZX-9501-A) with its 111⁄16-inch throttle bores was produced for low-displacement V-8s such as the Boss 302. The super-sized 1,425-cfm version (D0ZX-9510-B) with trash can–size 21⁄4-inch bores was sized more appropriately for big-blocks such as the 427.
Both carburetors were fitted with the same upper body air horn. It may surprise you to know that much of the In-Line four came right off the Ford parts shelf. Items such as the accelerator pumps were borrowed from the 2100 series Autolite 2-barrel.
The 221/260/289/302-2V engines all use the same basic cast-iron intake manifold. However, manifold castings differ considerably. The 221 and 260 engines are equipped with cast-iron dual-plane intake mani-folds with 1.60 x .84–inch runners. The 221’s carburetor base intake bores are 1.375 inches and the 260’s are 1.444 inches. The 289’s intake manifold runners differ also at 1.82 x .90 inches with 1.560-inch bores in 1963–1964 and 1.600 inches from 1965 to 1967. The 302’s dimensions are identical to the 289’s.
The 289-4V cast-iron intake manifold, first available in 1963, has the same-size runners as the 2-barrel manifold at 1.82 x .90 inches. All intake runners are 1.600 inches, just like the 2-barrel. This manifold was employed on all 289/302 4-barrels. The 351W-2V’s cast-iron intake manifold employed 1.82 x 1.02-inch ports with 1.640-inch throttle passages. The same holds true for the 351-4V.
Because the 351C-2V engine is so different architecturally than the 351W, its cast-iron intake manifold is completely different. The 351C-2V intake manifold has large 1.90 x 1.28-inch intake runners. By comparison, the 351C-4V intake manifold has 2.38 x 1.63-inch runners. Converting a 351C-2V to 4V is virtually impossible without an engine teardown because the ports don’t match.
The Boss 302 engine is just as different an animal as the 351C due to its enormous ports and poly-angle-valve heads. Its cast-aluminum Buddy Bar dual-plane intake manifold has the same 351C-4V 2.38 x 1.68–inch runners along with 1.76 x 1.76–inch throttle bores. They are large ports intended for high-RPM use. That’s why these engines lack low-end torque. To get low- to mid-range torque, you need port velocity (air speed) at low RPM. This is why the Boss 302 and 351C-4V engines are slugs at low RPM. Both engines were designed for high-RPM operation.
Factory Performance Manifolds
Easily the most popular factory performance intake manifold is the Cobra high-rise (C9OZ-9424-D), which was originally produced by Buddy Bar and available from Shelby American and Ford dealers back in the day. This manifold is the easiest small-block bolt-on there is and improves both horsepower and torque. It accommodates the Autolite 4100 or any of the square-flange Holleys. A similar dual-plane Cobra high-rise manifold is also available for the 351W.
Plenty of factory and aftermarket high-performance intake manifold options are available for the Boss 302. The Autolite In-Line four, also known as the Cross Boss in four- and eight-throat versions, is certainly the most unusual induction system ever available for the small-block Ford. The Cross Boss is a high-RPM rac-ing induction system not suggested for the street. However, it’s one heck of a conversation piece if you don’t mind street drivability issues. Also, because Autolite In-Line fours are rare, they’re also expensive, com-manding thousands of dollars. The Autolite In-Line four is a manifold and carburetor combination, which means you need both.
Although lots of aftermarket manifolds were made for small-block Fords, the best one is the highly collectible Edelbrock F4B cast in the 1960s and 1970s. It is virtually identical to the Cobra high-rise and offers an excellent balance of low-end torque and high-RPM power. Edel-brock quality in those days was out-standing with nice finish work. That makes the F4B a good-looking classic performance part.
If you want a nostalgic look underhood, go vintage all the way with original speed parts from the 1960s. Edelbrock wasn’t the only player. Hit the swap meets and check out Offenhauser, Weiand, Shelby, and a host of other performance manifold manufacturers from the golden era of street/strip insanity.
Fuel Pumps and Fuel Injection
Because there were so many variations of fuel pumps for small-block Fords, they cannot be covered in detail here. Two basic types were used (both Carter): one you can rebuild and one that is sealed. Rebuild kits are available for the rebuildable Carters. And believe it or not, there are rebuilders who can rebuild the sealed Carter pump. Information on these rebuilders can be found on the Internet.
From 1962 to 1965, small-block Carter fuel pumps had an integral can-style Rotunda fuel filter and fuel lines that were hard lined to the carburetor. Beginning in 1966, fuel filters became small and screwed into the carburetor with a fuel hose between line and carburetor. If you have a choice and aren’t picky about originality, go with the can-style pump and hard line to the carburetor in the interest of safety with today’s corrosive fuels. You’re not that concerned with fuel hoses that aren’t under pressure, but rather those that are under pressure. If you go with fuel hoses, use high-pressure hoses designed for both corrosive fuels and fuel injection systems.
Central Fuel Injection
Central Fuel Injection (CFI) first appeared on 5.0L small-block Fords in 1980 on top of either a cast- iron or aluminum 2-barrel intake manifold. The first Ford vehicle to have CFI was the Lincoln Versailles. Manifold selection was rooted in vehicle weight based on strict CAFE standards. If the vehicle was too heavy, Ford went with a cast-aluminum intake manifold.
Mustangs, for example, received the iron manifold instead of an aluminum one. Like carbureted engines, CFI engines were fitted with a spacer beneath the throttle body to accommodate the exhaust gas recirculation (EGR) valve and improve torque. Although these manifolds were nothing more than 2-barrel carburetor castings, they had unique Ford part numbers: E3AZ-9424-C for cast iron and E0VY-9424-A for aluminum.
The E3AZ-9424-C manifold is identical to the one that Ford used on the late-1970s 302-2V V-8. Although performance buffs tend to look down their noses at CFI, it’s a good idea for vintage Fords where fuel injection is desirable, but you want to keep it hidden.
CFI employed a central throttle body in place of a Motorcraft 2150 2-barrel carburetor with two injectors fitted in the bores above the throttle plates. It works basically the same way as SEFI (see below). A throttle position sensor (variable resistor) provides feedback on throttle position. A manifold air pressure (MAP) sensor provides manifold vacuum feedback. Oxygen sensors provide oxygen content feedback. A coolant temperature sensor provides coolant temperature feedback.
These sensors work together with an electronic control module (ECM) to control injector pulse width. Open the throttle and injector pulse width becomes more rapid to deliver more fuel. Ford used a conventional carburetor air cleaner with CFI.
In 1986, Ford came out with a unique fuel injection system called Sequential Electronic Fuel Injection (SEFI), a portinjection fuel system that thrust the venerable small-block Ford into a new era of crisp, reliable performance. SEFI was the result of years of development and testing. And as you might expect from Ford, the result was an exceptional fuel/air delivery system that has only become better with time because Ford never stops the engineering process. It is always an ongoing development process designed to improve performance and reliability while reducing emissions.
SEFI was a vastly different two- piece induction system that resembled a vacuum cleaner with 21-inch-long intake runners. It didn’t look as cool as Chevrolet’s Tuned Port Injection (TPI) system. However, it became a very successful engine fuel and ignition management system. Ford, faced with a distributor in front for easy access, had to approach tuned intake runners differently than General Motors did. Ford’s system, like GM’s, has an upper and lower intake plenum. However, Ford used longer runners for better low- to mid-range torque.
The lower intake manifold has eight electronically fired fuel injectors timed to inject fuel precisely when the intake valve opens. Injectors receive their fuel from two pressurized fuel logs with four injectors each. Return flow to the fuel tank is controlled via a vacuum-controlled fuel pressure regulator.
From 1986 to 1993, the 5.0L SEFI engine’s upper intake manifold didn’t change much. For 1986, it’s a stand-alone with smaller runners. For 1987–1993, runners are larger allowing better airflow for improved horsepower. In 1994, the Mustang had a lower hoodline with strut tower bracing for stiffness. This meant that Ford engineers had to develop a new upper intake manifold for the new SN-95 Mustang GT. With this new upper manifold came less performance due to smaller, lower intake runners. When coupled with Mustang’s increased weight, performance suffered. Less horsepower, yet more torque.
Throughout the rest of the Ford car lines, the 5.0L High Output engine’s induction system didn’t change much from 1986 to 1992.
In 1993, Ford’s SVT kicked Mustang performance up a notch with the limited-edition Cobra hatchback. The first thing was to improve induction and cylinder heads with the GT-40 package on top: GT-40 cylinder heads and induction system. The GT-40 induction system (Ford Racing PN M-9424-D51) is identifiable by its staggered round ports and runners. This part number is the same package that came on production 1993 Mustang Cobras, which makes it different than the aftermarket GT-40 package also available from FRPP.
The M-6001-A50 GT-40 kit from Ford Racing is plentiful, used and still available new from any FRPP dealer. Because the M-6001-A50 kit is unique, upper and lower intake manifolds must be used together. The individual parts carry PN M-9461-A50 (for the lower) and PN M-9424-A51 (for the upper).
If you’re building a 351W/5.8L with SEFI and want GT-40 performance, a special lower manifold from Ford Racing (M-9461-A58) is compatible with the GT-40 M-9424-A51 upper intake manifold.
Ford used at least three types of injectors in more than 25 years of fuel-injected engines. The one that has been used most in fuel-injected small-block Fords is the EV1 with the two-pin Jetronic/Minitimer plug.
Most 5.0L engines received the orange 19-lbs/hr EV1 injector. The EV1 Ford/Bosch injector is identified by color.
The Ford/Bosch color-coding system does not apply to all fuel injectors. It is not an industry standard, but instead a corporate standard within Ford and Bosch for quick identification.
Written by George Reid and Posted with Permission of CarTechBooks