All 221, 260, 289, 302, 351W, and 351C 2-barrel engines were originally fitted with dual-plane iron intake manifolds and the venerable Autolite 2100-series 2-barrel carburetor from the factory. Although some of them have been replaced with aftermarket 2-barrel Holley or Carter carburetors, there’s no better 2-barrel than the 2100. The beauty of the 2100 is its simplicity and ease of service. Easy to service and tune, it rarely complains and goes longer than any other carburetor between overhauls. The 2100 carburetor was first introduced in 1957 and remained in production, as the 2150, until the 1980s. The 2100’s bigger brother, the Autolite 4100 4-barrel, operates on the same basic principle as the 2100, but with a pair of secondary throttle bores for hot acceleration. The 4100 was replaced by the 4300 Autolite emissions carburetor in 1967.
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Although the 4100 didn’t set any land-speed records, it is easily the most reliable carburetor ever made. The same can be said for the 2100. The 4100 offers the same benefits as a comparable Holley 1850/4150/4160, in sizes ranging from 480 to 600 cfm. You can run the 4100 on your aftermarket manifold and get the same kind of performance you’d get from a same-sized Holley. And Holley carburetors make good drop-in replacements for the 2100 and 4100 without losing reliability. The Holley 1850/4150/4160 are easy carburetors to maintain and service. In fact, Classic Tube makes a custom fuel line for Holley carburetors on small-block Fords.
Induction systems for the smallblock Ford are simple to understand— simple dual-plane cast-iron manifolds topped with one basic type of carburetor. Identification is straightforward and based on throttle bore size. For example, a big-block Autolite 2100 has larger throttle bores than those for a smallblock. A big-block 2100’s throttle plates do not open to capacity on top of small-block. Likewise, a small-block 2100 stifles a big-block. Carburetor type/size is determined by venturi diameter, which is cast into the left-hand side of the body near the accelerator pump. You can expect to see .98, 1.01, 1.02, 1.14, and 1.23, which represent the venturi diameter in inches.
Although the 221 was only in production for a short time (1962–1963), it had eight possible 2100 carburetor types, with the smallest having .98-inch diameter venturis with 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 upon application. Venturi size depends on transmission, vehicle application, and the original seller’s sales district. California emissions carburetors were originally jetted differently than those in the other 49 states. This was also true for high-elevation destinations like Denver, where jetting was leaner. For 1964, the 289 received stilllarger venturis to improve power—1.14 inches for 300 cfm. This improved lowand 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 body. The most significant changes came in 1964, with an improved accelerator pump, choke unloader, and national pipe threads (plumbing-type) at the fuel inlet. More positive changes came in 1966 with the deletion of brass fuel bowl vent tubes. In 1970, in an effort to reduce emissions, a choke unloader diaphragm was added to the air horn to improve coldstart performance.
The 289 high-performance V-8, introduced in 1963, was the first small-block Ford equipped with an Autolite 4100 carburetor, originally with an automatic choke and choke heat tube. The Hi-Po later received a manual choke on its veryhard- to-find 4100. When the Mustang was introduced in the spring of 1964, Ford introduced the one-year-only 289-4V lowcompression, regular fuel V-8, also with the 4100 carburetor having 1.08-inch venturis at 480 cfm. The Hi-Po got a larger 1.12-inch diameter venturi carburetor with 600 cfm at wide-open throttle.
Deteriorating air quality in major US cities started getting the attention of environmentalists and Washington alike in the mid 1960s. Los Angeles, in particular, had dangerous air quality during hot summers, posing a significant health risk to the masses. Something had to be done. Ford set its sights on improving exhaust emission levels. Some of it was voluntary. Some of it was mandated by Washington. The Autolite 4300 4-barrel carburetor was conceived to reduce emissions and improve performance.
The 4300 was never an easy carburetor to service and tune. Not even Ford could get it to function properly. It suffered, and continues to suffer from stumble and hesitation. Ford struggled with the 4300, with significant modifications each and every year. For one thing, the 4300 differed a lot from the shoebox 4100 it replaced. It has larger secondary throttle bores and small primaries. From the very start, there were operational problems with this carburetor. If you’re frustrated with your 4300, you’re not alone. That first year (1967), there was only the single 441-cfm size—not enough carburetor. For 1968, a larger 600-cfm 4300 was introduced for big-block applications only. The 441-cfm 4300 was dropped in 1970. In 1974, the 600-cfm 4300 was dropped in favor of the redesigned 4350, which was just as frustrating.
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, much like the Carter Thermo Quad, Rochester Quadrajet, and Holley Spread Bore. The 4300D was big on fuel delivery at wideopen throttle. It can be safely said the 4300D is a very temperamental carburetor. Also, it is not interchangeable with any other type of carburetor, which means carburetor and manifold are married and must be used together. Forget using a Holley Spread Bore or Rochester Quadrajet because they do not fit. The key here is learning how to live peacefully with this carburetor.
The 4300 and 4300D are identified by Ford part numbers cast into the body. So if the identification tag has been lost, these numbers are located in the base at the left-front part of the carburetor. The greatest challenge with the 4300 is to understand how it works. Performance depends on proper calibration. The 4300 has mechanical secondaries like the Rochester Quadrajet, and unlike the 4100, which has vacuum secondaries. As the throttle is stabbed and the secondaries open, air valves on top should follow suit smoothly for a nice transition to full power. However, rarely does this happen 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 leanness for reduced emissions in normal driving. Pony Carburetors, Inc., has improved the 4300’s driveability problems; however, there are no guarantees. The proof is there when you install the 4300 or 4300D and you see how it performs under actual driving conditions.
Motorcraft Variable Venturi (VV) Carburetor
Although I hope you never have to deal with one of these, I know some people inevitably will. The Motorcraft Variable Venturi (VV) 2-barrel carburetor was an honest effort by Ford to reduce emissions. However, it has proven to be even more challenging than the 4300 and 4350 carburetors. It is expensive and it’s hard to service. If you have to buy a rebuilt VV carburetor, they’re priced around $1,000 at most auto parts stores, if they can even get them. If you attempt to rebuild one yourself, your success is a crapshoot at best. I suggest a Ford Shop Manual and a lot of patience.
The Motorcraft VV carburetor was first introduced in 1977 on Ford’s 2.8L V-6. It appeared on the 302 Ford in 1979, where it was used until 1982 on all California- bound vehicles with this engine. The 255-ci small-block also got the VV carburetor. Although the VV carb 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 upon throttle position and load. It has main metering rods and jets like a Carter carburetor. As the throttle is pressed, tapered metering rods allow more fuel to flow. VV carburetors are identifiable by identification codes stamped into the upper body. When the identification tag is gone, stamped codes are the only means to identification.
The Holley 4150 witnessed very little factory use on small-block Fords, and only on Shelby Mustang and Boss 302 Mustang/Cougar. Shelby American used the very-limited-production center-pivot LeMans bowl 715-cfm Holley 4150 on its GT350 Mustangs with 289 High Performance V-8s. Ford went with the 780-cfm Holley 4150 atop the Boss 302 engine in 1969–1970. These carburetors received a Ford part number their first year out in 1965, and then got a Shelby part number through 1967. The Boss 302 Holley 4150 got a Ford part number along with a Holle List Number. These part numbers, 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 Holley list number confirms exactly what you have.
Shelby’s 4150 has a secondary metering block and flows 715 cfm at wideopen throttle. For 1968, Shelby GT350s received the 600-cfm 4150 Holley 4-barrel carburetor. Later in the model year, they got the Autolite 4300 as a means to cutting costs and reducing emissions.
There are a few rules with factory Holley carburetion. The 4150 has both primary and secondary metering blocks. The 4160 has only a primary metering block. Factory Holleys 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 Mustang GT and Capri RS came the Ford/Holley 4180-C 4-barrel carburetor on top of 5.0L high-output V-8s with 4- and 5-speed manual transmissions. Automatic versions got Central Fuel Injection (CFI).
The 4180-C carburetor isn’t your typical Holley 4-holer. It is a unique 600-cfm carburetor with anti-tamper technology. It is not computer controlled. Although the 4180-C is an anti-tamper carburetor, it can be tampered with 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 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, with different jet size markings.
Performance improvements with the 4180-C are off-the-shelf Holley tried-andproven techniques. Jet upsizing. Power valve swaps. Accelerator pump adjustment. Fuel filter removal. These steps improve performance. Swapping the primary metering block is impossible because it is unique to the 4180-C.
You can always shelve the 4180-C and install a conventional Holley 4150/4160. However, be advised you’re wrestling with smog laws in many states. Your 5.0L High Output must be able to pass a visual smog check to get licensing in most states. Not all states have jumped on the visual inspection bandwagon, however.
Several multiple carburetion setups were available from Ford for the smallblock early in their history. The three 2-barrel (tri-power) and two 4-barrel (dual quad) set-ups were available through Ford dealer parts departments as aftermarket performance accessories. Manifolds were produced by Buddy Bar. Carburetion was always Holley. Tri-power set-ups employed three aft facing Holley 2-barrel carburetors, with the center carburetor fitted with a choke for cold starting.
Here’s what to look for with threedeuce setups. Two basic configurations were available from dealers. The 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 1965–1966, 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 (together) flow approximately 1,000 cfm at wideopen throttle.
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 manifolds with 1.60 x .84-inch runners. The 221’s carburetor base intake bores are 1.375 inches, while the 260’s are 1.444 inches. The 289’s intake manifold runners differ yet again at 1.82 x .90 inches with 1.560-inch bores in 1963–1964 and 1.600- inch in 1965–1967. The 302’s dimensions are identical to the 289.
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-barrel engines. The 351W-2V engine’s cast-iron intake manifold employed 1.82 x 1.02-inch ports with 1.640-inch throttle passages. The same can be said for the 351W-4V.
Because the 351C-2V engine is sodifferent architecturally from 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 are so mismatched.
The Boss 302 engine is just as different as the 351C due to its enormous ports and poly-angle valve heads. Its cast-aluminum Buddy Bar dual-plane intake manifold has those same 351C-4V 2.38 x 1.68-inch runners along with 1.76 x 1.76-inch throttle bores. These 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
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. This manifold is undoubtedly the easiest small-block bolt-on there is and improves horsepower and torque. A similar dual-plane Cobra high-rise manifold is also available for the 351W.
The Boss 302 enjoys a wealth of factory and aftermarket high-performance intake manifolds. The Autolite in-line four, also known as the Cross Boss in four and eight-bore versions, is certainly the most unusual induction system ever available for the small-block Ford. The
Cross Boss is a high-RPM racing induction system not recommended for the street. However, it’s one heck of a conversation piece if you don’t mind street drivability issues. And one more thing: because Autolite in-line fours are relatively rare, they’re also expensive. The Autolite in-line four is a manifold and carburetor combination, which means you need both in order for it to work.
Although lots of aftermarket manifolds were made for small-block Fordsway back when, the best manifold out there is the collectible Edelbrock F4B made 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. Edelbrock quality in those days was outstanding 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, and a host of other performance manifolds from the golden era of road and drag racing.
Central Fuel Injection Manifolds
Central Fuel Injection (CFI) first appeared on small-block Fords in 1980 on top of either a cast-iron or aluminum 2-barrel intake manifold. In fact, the first Ford vehicle to have it was the Granadabased Lincoln Versailles. Manifold selection was rooted in vehicle weight and based on strict corporate average fuel economy (CAFE) standards. If the vehicle was too heavy, Ford went with a castaluminum intake manifold. Mustangs, for example, got the iron manifold. Like carbureted engines, CFI engines used 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 manifold is identical to what 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 as hidden as possible.
CFI involved a central throttle body in place of a Motorcraft 2150 2-barrel carburetor, with two injectors fitted above the throttle plates. It works basically the same way as Sequential Electronic Fuel Injection (SEFI). A throttle position sensor (variable resistor) provides feedback on throttle position. A manifold air pressure sensor (MAP) provides manifold vacuum feedback. Oxygen (O2) 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 the injector pulse width becomes more rapid to deliver more fuel. Ford used a conventional carburetor air cleaner with CFI.
5.0L/5.8L SEFI Induction System Manifolds
In 1986, Ford came out with a fuel system none of us had ever seen before, known as Sequential Electronic Fuel Injection (SEFI), a port-injection 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 gotten 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 power-rug attachment with 21-inch-long intake runners. It didn’t look as cool as Chevrolet’s Tuned Port Injection (TPI) system. However, it panned out to be 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 went with 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 get their fuel from two pressurized fuel logs, four injectors each, where return flow to the fuel tank is controlled via a vacuumcontrolled fuel pressure regulator.
From 1986–1993, the 5.0L SEFI engine’s upper intake manifold didn’t change much. For 1986, it was a standalone with smaller runners. For 1987–1993, runners are larger allowing better airflow for improved horsepower. In 1994, Ford was faced with a lower Mustang hoodline with strut-tower bracing for stiffness. This put Ford engineers in the position of having to develop a new upper intake manifold for the new SN-95 Mustang GT. With this new upper manifold came disappointing 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 carlines, the 5.0L High Output engine’s induction system didn’t change much from 1986–1992.
In 1993, Ford’s Special Vehicle Team (SVT) kicked Mustang performance up a notch with the limited-edition Cobra hatchback. 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 Part Number M-9424-D51) is identifiable by its staggered round ports and runners. This part number is the same identical package that came on production 1993 Mustang Cobras. This also makes it a bit different than the aftermarket GT-40 package also available from Ford Racing Performance Parts.
The M-6001-A50 GT-40 kit from Ford Racing is out there in plentiful numbers used, and is still available new from any Ford Racing Parts dealer. Because the M-6001-A50 kit is unique, upper and lower intake manifolds must be used together. These components separately are M-9461-A50 for the lower and M-9424-A51 for the upper.
If you’re building a 351W/5.8L with SEFI and want GT-40 performance, there’s a special lower manifold from Ford Racing (M-9461-A58) that’s compatible with the GT-40 M-9424-A51 upper intake manifold.
Although Ford has used at least three types of injectors in more than 25 years of fuel-injected engines, let’s focus on what has been used most in fuel-injected smallblock Fords. The most common fuel injector 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. Colors go as follows:
Orange = 19 lbs/hr
Light Blue = 24 lbs/hr
Red = 30 lbs/hr
Dark Blue or Silver = 36 lbs/hr
Green = 42 lbs/hr
This 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.
Thermactor Emissions System
When California air pollution standards got tougher in the mid 1960s, Ford started taking clean emissions seriously. Although Ford went to a closed crankcase ventilation system on California cars beginning in 1964, it wasn’t enough. Neither were leaner jetting and a faster choke pulloff. Something had to be done that wouldn’t do engine damage (lean mixture) or hurt performance, and yet improve exhaust emissions.
Ford’s answer was Thermactor: an air pump system designed to inject oxygenenriched air into each exhaust port, where unburned hydrocarbons could be burned before being expelled into the atmosphere. Although this system didn’t work very well over time and with use, it did reduce emissions. Thermactor is very simple, consisting of the air pump (most call it a smog pump), belt drive, hoses, antibackfire valves, and air-injection manifolds. Thermactor parts are very hard to find because so many of them were thrown away in the old days. However, the reproduction aftermarket does make some parts such as the air-injection manifolds, hoses, and anti-backfire valves. Antibackfire valves allow the flow of air in one direction only, which protects the pump.
Because there were so many variations on fuel pumps with small-block Fords, I only reference them briefly here. Two basic types were used (both from Carter): one you can rebuild, and one that is sealed. Rebuild kits are available for the rebuild-capable Carters. And believe it or not, there are rebuilders out there who can rebuild the sealed Carter pump. Information on these rebuilders can be found on the Internet.
From 1962–1965, 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, I suggest you go with the canstyle pump and, with today’s corrosive fuels, hard line to the carburetor in the interest of safety.
You need not be concerned with fuel hoses that aren’t under pressure, but those that are under pressure. If you go with fuel hoses, use high-pressure hoses designed for corrosive fuels and fuel-injection systems.
When the time comes to plumb your small-block’s fuel system, you can custom- bend your own lines with easy do-ityourself tube bending and flaring kits from The Eastwood Company. However, did you know Classic Tube has complete, pre-bent fuel line kits for Fords, Mercurys, and Lincolns of all types? Perhaps you’ve installed a Holley 4150 or 4160 on your small-block? Classic Tube has pre-bent lines ready to install. And this is not just the engine, but also chassis lines as well, with tubing available in galvanized or stainless steel.
The down side to stainless steel is getting flares to seat perfectly the first time around. Stainless lines will leak at first—count on it. However, if you loosen them and tighten them firmly and repeatedly, they will seat and stop leaking. You just have to stay at it. When they leak, you loosen and tighten until the eaks stop. Don’t forget to inspect both the line flare and the fitting for damage. Even a small nick will leak. Fuel line size is a very important issue most of us miss. Those small, factory 5/16-inch fuel lines are inadequate if you’ve got a small-block making 500 hp.
Every square inch of fuel line from tank to carburetor must be the same size. If you’re running a 500-horse small-block with 5/16-inch fuel line anywhere between tank and carburetor, your engine will be fuel starved at high RPM. That means a lean mixture and engine damage.
If you’re running anything making 300+ hp, you must have 3/8-inch fuel line from tank sending unit to the carburetor. If you have 5/16-inch line between the tank and fuel pump, and 3/8-inch between pump and carburetor, you still have 5/16-inch fuel line. Line and hose size must be uniform from bumper to bumper for proper operation.
Written by George Reid and Republished with Permission of CarTech Inc