Ford’s popular small-block V-8 engine began its production life at 221 ci with a 3.500-inch bore and 2.870-inch stroke topped by an Auto-lite 2100 2-barrel carburetor with automatic choke. What made the small-block Ford innovative was its lightweight gray iron and thin-wall construction, which made efficient V-8 power available in compact and intermediate-size cars.

Because the small-block Ford engine was an “oversquare” design, meaning bore size was larger than stroke, it received larger valves along with reduced reciprocation speed and shorter connecting rods, allowing higher RPM. Plenty of iron content in the main webs allowed for the elimination of block skirts found in earlier Ford V-8 designs, which reduced engine weight. The small-block Ford V-8 was a quantum leap in lightweight cast-iron engine technology at the time.

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The small-block Ford was produced in two foundries and engine plants during its long production life: Cleveland, Ohio, and Windsor, Ontario. The 351W was produced exclusively at Windsor. The 221 and 260 were produced at Cleveland only. The 289 and 302 were produced at Windsor and Cleveland, which can be verified by “CF” and “WF” casting marks on heads and blocks.

According to Ford small-block historian Bob Mannel, more than 500 prototype and preproduction 221-ci engines were dyno tested and evaluated before Ford began mass production, logging 17,000 hours in Ford’s Dearborn Dynamometer Laboratory and 250,000 miles of in-vehicle testing. The 221 and 260 were introduced in the 1962 Ford Fairlane and Mercury Meteor. During the following years, the 221 and 260 proved to be fiercely reliable engines that were both peppy and economical to operate.

Although these engines are virtually identical externally, there are differences that make them identifiable. The 221 had a hub/pulley adaptor and counterweight. The 260 had a true harmonic dampener. From 1962 to 1965, small-block Fords were identified by engine color: color-coded valvecovers and air cleaners over a black block and heads. All Ford engines were primarily black with valvecovers and air cleaner in specific colors for identification purposes. Beginning in 1966, all engines were painted Ford Corporate Blue and remained that way until the early 1980s when the color changed to gray, then ultimately bare iron and aluminum. Early on, the 221/260 had a timing cover oil filler tube, which was used in production through 1964. Not all engines were equipped this way. Others had a valvecover oil filler neck.

221

The 145-horse 221-ci V-8 was introduced in 1962. It was a very low-displacement small-block that has very little interchangeability with the 260, 289, 302, and 351W V-8s. It is fitted with the 2.870-inch cast crankshaft yet with no identification mark like the 289’s “1M” crank, which didn’t happen until 1963.

260-2V V-8 in light blue over black in a 19641⁄2 Mustang. 

1964 289-2V V-8 in red over black in a Fairlane.

289-4V V-8, regular fuel, gold over black, in a 19641⁄2 Mustang with timing cover oil filler.

Here’s the Mustang-only 1964 1⁄2 289-4V low-compression V-8 with valvecover oil filler cap and PCV valve. When these engines had the timing cover oil filler tube, they were not fitted with a PCV valve. Instead, they had the draft tube extended from the rear of the intake manifold or off the passenger-side valvecover. Three or more variations were produced.

 

Connecting rods were “C2OE” forgings of the same length as the 260 and 289. However, these forgings were dropped for the stronger “C3AE” rod of 1963. The 221’s very modest cylinder heads employ small ports and wedge 43.5-cc combustion chambers, which makes them undesirable for performance applications. These cylinder heads are non-players unless you are performing a restoration and want original castings. Compression ratio with 221 heads with the 260/289/302 was too high, making them unacceptable.

The 221-ci small-block was short- lived with production ending in 1963.

260

Introduced at the same time as the 221 (in 1962), Ford’s 260-ci small-block made 164 hp via larger 3.800-inch bores and the same 2.870-inch stroke. Like the 221, the 260 was fitted with the cast crank with 2.870-inch stroke devoid of any markings that first year. It was also fitted with the C2OE connecting rod until mid-1963 when it received the stronger C3AE forging. The 260’s cylinder heads had larger 53-cc chambers with the same 1.590/1.390-inch valve sizing of the 221. Valvestem size also stood at 0.310 inch, just like the 221’s.

The 260 was available only with Autolite 2100 2-barrel carburetion with automatic choke. Both the 221 and 260 were mild-mannered mills at 8.7:1 compression with cast pistons for use with regular leaded fuels of the era. Carroll Shelby launched two-seat Cobra production with the 260-ci small-block topped with a Cobra high-rise manifold and Holley carburetion.

The 260 was also short-lived with production ending in 1964.

289

Ford increased bore size to 4.000 inches to conceive the 289 in 1963 while staying with the small-block’s original 2.870-inch stroke and cast crank. The 289 can easily be viewed as one of Ford’s most successful engines thanks to an incredible performance history at LeMans, Indianapolis, Sebring, Daytona, and dozens of other racing venues around the world.

You cannot take the 260’s 3.800-inch bores to 4.000 inches to make it a 289 because cylinder wall thickness becomes compromised. You have to begin with a 289 or 302 block. The 289 block is a thicker casting designed for larger 4.000-inch bores. The same can be said for the 302 block, with its extended cylinder skirts (extended by .015 inch), which came later in 1968. In fact, the 302 block first showed up in the 1967 model year stuffed full of 289 internals: the 1M crank with 2.870-inch stroke with C3AE rods and cast pistons.

There are many misconceptions about the 289. It is time to set the record straight. All 289 cylinder heads, including High Performance, have the same port, valve, and chamber dimensions. Intake valves are 1.780 inches. Exhaust valves are 1.450 inches.

This is a 1965 289-4V V-8 in gold over black, premium fuel, with California emissions closed-crankcase ventilation in a Mustang. All small-blocks originally delivered to a California sales district had closed-crankcase ventilation.

The 1965 289 High Performance V-8 yielded 271 hp at 6,000 rpm. It was unavailable with automatic transmission until 1966 in the United States. Most were fitted with the castiron Ford Top Loader 4-speed transmission. 

What makes the 289 High Performance head “high performance”? The valvespring pockets for stability along with screw-in rocker arm studs engineered to withstand high RPM. Otherwise, 289 High Performance heads aren’t any different than standard 289 castings. If you desire the features of 289 High Performance heads without the price, you can upgrade the 2V/4V head to screw-in rocker arm studs with pushrod guide plates and valvespring cups. You get the same result for less money.

In the 289’s first year, 1963, two basic engines were available: a 2-barrel version with Autolite 2100 carburetion as in the 221 and 260, and the 289 High Performance with Autolite 4100 4-barrel automatic choke carburetion and mechanical tappets, 9.0:1 compression, castiron exhaust headers with automatic choke heat stove, and 289 High Performance–specific heads.

In 1964, Ford added a third 289 to the mix. It had 4-barrel carburetion and the same compression ratio as the 2-barrel available in Mustangs only (D engine code).

This is Ford’s 289 High Performance V-8 with closed crankcase ventilation California emissions package and a PCV valve (not visible). Some Hi-Po engines were clad with the “Cobra Powered” valvecover sticker. It has yet to be proved whether this was added at the factory or a dealer parts counter.

Beginning in the 1966 model year, all Ford engines were clad in Ford Corporate Blue, which was a move to identify them as Ford engines. This is a 1966 289 produced prior to May 1966 with traditional small-block Ford valvecovers. 

California emission standards manifested themselves two ways in 1964: closed crankcase ventilation coupled with the use of a positive crankcase ventilation (PCV) valve, the latter also used on most 49-state cars. There’s no rhyme or reason as to how these engines were equipped and distributed, besides the California emissions closed crankcase ventilation system. Some 289 engines were fitted with PCV valves while others were fitted with a draft tube. Some 1964 289 engines were fitted with timing cover oil filler tubes, while most were located in the driver-side valvecover.

Combustion chamber sizes in 1963–1964 ranged from 52.6 to 55.6 cc for all 289 engines. Chamber size depended upon the casting. All 1963–1964 289 engines had five-bolt bellhousing blocks just like the 221 and 260.

Mid-Year Changes

Important upgrades in the 289 occurred for the 1965 model year beginning in August 1964. The most obvious was a block casting change from a five-bolt bellhous-ing pattern to a six-bolt to improve noise, vibration, and harshness. Aside from this important change, the 289 remained essentially the same, with the base 289-2V engine retaining 52.6- to 55.6-cc combustion chambers and dished pistons to keep compression at 9.0:1. Valve sizes remained the same.

The 289-4V engine went from sharing dished pistons and the same compression ratio to 10.0:1 and flat-top pistons for 1965. All pistons, flat-top and dished alike, had valve reliefs. The 289 High Performance V-8 remained virtually unchanged aside from the six-bolt bellhousing block and a higher compression ratio.

As of May 2, 1966, Ford went to a rail-style rocker arm and pent-roof (flat-top) valve covers on 289-2V/4V engines, which continued through the 1967 model year. This 289-4V engine has California emis-sions closed crank-case ventilation.

For 1968, Ford went to a pent-roof “Power By Ford” valvecover as well as a redesigned air cleaner assembly for 289/302 engines, all with closed crankcase ventilation for 50-state use. The 289/302 also were equipped with Improved Combustion  (IMCO) with a coolant temperature–activated spark timing vacuum control valve. This is the “J” code 302-4V V-8 with Autolite 4300 carburetion in a 1968 Mustang.

Shown is a 1970 302-2V V-8 with the same basic small-block Ford air cleaner introduced in 1968. Beneath this air cleaner is a more emissions-friendly Autolite 2100 carburetor with evaporative emissions and a more aggressive choke pull-off.

The 289 didn’t change for 1966 aside from engine color. California emission standards became tougher for 1966, calling for not only closed crankcase ventilation, but also Ford’s Thermactor air-injection pump system to help completely burn hydro-carbon emissions.

Effective May 2, 1966, 289-2V and 4V engines received important cylinder head and valvetrain changes: rail-style rocker arms, longer valve- stems, revised cylinder head castings, and pent-roof (flat-top) valvecovers. The pent-roof-style valvecovers were in production through the 1967 model year.

One subtle change during the 1966 model year was the short-term use of a finned timing cover through early 1967. Although the 289 High Performance V-8 never employed rail-style rocker arms, it did use pent-roof valvecovers with a chrome finish and High Performance open-element air cleaner for 1967.

Production of the 289 ended in 1968.

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302

Ford’s 289-ci V-8 witnessed such great success across the board as both a fiercely dependable street engine and a world-beating performer on the racing circuit that you wouldn’t think Ford would disturb this success, but it did with a small increase in stroke. Pressure from increasing displacements at Chevrolet, Pontiac, and Chrysler pushed Ford toward adding more stroke to the tried-and-proven 289 to get 302 ci.

The additional stroke was chal-lenging to measure at .013 inch, bringing the small-block Ford’s stroke to 3.000 inches. Ford had to revise the block, extending cylinder skirts .015 inch for improved piston stability at bottom dead center. Some 1967–1968 289 engines received 302 blocks as early as February 1967. This was toward the end of the 1967 model year before the 302 entered production.

Although the 302 has a longer 3.000-inch stroke, it has a shorter C8OE connecting rod (5.090 inches center-to-center); it is not interchangeable with the C3AE 221/260/289 rod (5.155 inches center-to-center). The 302’s shorter  rod, when combined with the longer 3.000-inch stroke 2M crankshaft, gives this engine its increased displacement. Aside from those small differences, the 302 is virtually identical to the 289, including valve size and combustion chamber design.

One exception is the 1968-only 302-4V “J” head with smaller 53-cc chambers and higher compression.  It is higher compression (premium fuel) because compression is the easiest means to increased power. What makes 1968 engines visually different than 1967 are the words “Power By Ford” stamped into their pent-roof valvecovers. These words appeared on all Ford valvecovers that year and continued until 1975 when they were replaced by the Ford corporate oval.

The 302 has evolved considerably since its introduction in 1968. Beginning in 1978, Ford changed the engine’s designation from a “302-ci” to “5.0-liter” (5.0L) V-8 as the United States became pressured to employ the metric system. In 1978, Ford also began fitting the 302 and other engines with a stamped aluminum air cleaner to reduce vehicle weight.

When Ford reintroduced the Mustang GT in 1982, it fitted the timeless pony with a High Output version of the 5.0L V-8. Although quite tame by today’s standards, the 5.0L High Output had a high-performance 351W Marine camshaft (and 351W firing order) coupled with a Motor-craft 2150 2-barrel carburetor and dual-snorkel aluminum air cleaner. The bottom end also changed to accommodate the increase in performance. Instead of the 289/302’s 28-ounce offset dynamic balance,  the 5.0L High Output had a 50-ounce  offset balance, which is very important to remember when you’re building these engines. Get it mixed up and you have unwanted, severe engine-punishing vibration.

In 1983, Ford began fitting the 5.0L High Output V-8 with the Holley 4180 4-barrel carburetor, which was a Holley-designed, Ford-engineered performance/emissions/tamper-proof carburetor. This carburetor, aside from minor engineering changes, remained essentially the same through 1985 along with the proven Motorcraft Duraspark II ignition system. In 1985, the 5.0L High Output V-8 received an all-new roller-tappet block designed to accommodate roller cam technology to improve both power and fuel efficiency.

Beginning in 1971, Ford’s 302-ci small-block received this smaller redesigned air cleaner assembly, which was in production through 1976.

Beginning in the 1977 model year, Ford fitted all of its small-blocks with aluminum air cleaners for weight- reduction purposes. This is a 1978 5.0L-2V small-block in a Mustang II with the Motorcraft 2150 emissions 2-barrel carburetor and Duraspark ignition.

Ford introduced the 5.0L High Output Sequential Electronic Fuel Injection (SEFI) in 1986 with 62- to 65-cc “High-Swirl” chambers and 200 hp on tap. It remains unknown 30 years later why the “5.0L Liter HO” graphics were sideways on these.

For 1987–1993, the 5.0L High Output SEFI V-8 delivered 225 hp and 300 ft-lbs of torque thanks to induction and cam improvements coupled with the fast-burn–chamber 1985 truck head.

Here’s the 240-horse 1994–1995 SVT Mustang Cobra 5.0L V-8 sporting GT-40 cylinder heads and induction. The GT-40 cylinder head was produced in cast iron and aluminum, available from Ford Motorsport SVO and Ford Racing.

This is the 1994–1995 5.0L High Output V-8 with the low-profile induction system for hood clearance, which hurt horsepower, yet improved torque.

In 1986, the small-block Ford received the most dramatic change in its history: port fuel injection. Known as Sequential Electronic Fuel Injection (SEFI), this new system of fuel delivery and spark control (EEC-IV) was the single biggest quantum leap in technology for the Fairlane V-8 because it wasn’t just port fuel injection, but complete electronic engine management. The 1986 5.0L High Output was fitted with “highswirl” chamber cylinder heads and experienced a loss in horsepower and an increase in torque.

Although the 5.0L SEFI High Output engine was intimidating for enthusiasts in the beginning, people ultimately embraced this power plant and went racing with a new attitude known as “PRO 5.0,” building powerful Mustang rocket ships. It was so successful that it spawned a new organization known as the National Mustang Racers Association (NMRA), which has become a huge Mustang subculture. This was an exciting new chapter for the industry that, at press time, shows no signs of fading away. Despite a drastic blow to the economy, enthusiasts are still racing the 5.0L small-block Ford in record numbers.

The 5.0L High Output V-8 has grown to become one of the most respected high-performance engines of our time.

In 1987–1993, Ford went back to the tried-and-proven fast-burn–chamber cylinder head, which was actually a truck casting that worked very well with SEFI, netting an increase in horsepower and torque.

255

Like the rest of Detroit in the late 1970s, Ford looked for ways to squeeze more mileage from a gallon of gasoline. The 255-ci (4.2L) small-block, which was produced at Ford’s Windsor, Ontario, foundry and engine plant, was a short-lived answer to a long-term challenge: fuel economy. Produced from 1980 to 1982 only, the 255 never cultivated a performance image because that’s not what it was designed to do. It was the only V-8 engine available in the Mustang in 1980–1981.

The baby Ford small-block has the same 3.000-inch stroke as the 302 with a smaller 3.680-inch bore. It has 255-specific cylinder heads with smaller combustion chambers and valves with round ports and absolutely no performance potential whatsoever. The 255 also had its own unique, lightweight hollow-core nodular iron crankshaft, yet with the 302’s 5.090-inch rods.

The 255 was a very short-lived chapter in small-block Ford history and one of the most forgotten engines of our time. It was fitted with either the 49-state Motorcraft 2150 carburetors or the California-only Motorcraft VV carburetor.

351W

Ford enthusiasts have long called the 221, 260, 289, and 302-ci engines “Windsor” V-8s. However, the only true “Windsor” engine is the 351-ci raised-deck small-block Ford intro-duced in 1969 as a response to the cubicinch race going on in Detroit. Even though the 221/260/289/302 engines were manufactured at Ford’s Cleveland engine plant, there are crossovers that require clarification. Not all 289/302 blocks and heads were cast at the Cleveland foundry. Quite a few were also cast at Windsor with a “WF” in the casting. Cleveland castings received a circled “CF.” Some blocks were devoid of any kind of foundry identification, which makes it tricky to identify them.

To achieve the 351’s displacement, Ford had to raise the 302’s deck 1.28 inches to accommodate the 3.500-inch stroke. Bore size remained the same at 4.000 inches. To improve power, smoothness, and reliability, Ford gave the 351W a different firing order than the 221, 260, 289, and 302 engines. Beginning in 1982, the 302 (5.0L) received the 351W’s firing order for the same reasons with the flat-tappet Marine camshaft. Ford insiders from the period tell me that the 5.0L engine was switched to the 351W’s firing order to more equally distribute stresses across the crankshaft.

The 351W employs a thicker walls around cylinder bores and main webs. Interchangeability with other small-block Fords is considerable, enabling all kinds of swaps. The 351W, for example, has the same six-bolt bellhousing bolt pattern as the 289/302 six-bolt blocks, making it possible to swap this engine into 289/302-powered vehicles. The 351W also accepts 289/302 engine mounts. Cylinder head bolt and bore patterns make head swaps straightforward.

Where it becomes challenging is 351W cooling passages between intake manifold and cylinder heads. Early 351W cylinder heads have dog-leg cooling passages, making it necessary to modify intake manifold gaskets and passages. The 351W’s cylinder heads are a great budget horse-power swap for 289 and 302 engines because they employ the same block deck patterns. These desirable heads have larger ports, valves, and chambers. Larger chambers have reduced compression ratio. Keep this in mind anytime you’re considering a head swap.

Ford raised the 302 block deck 1.28 inches to conceive the 351-ci Windsor V-8 for 1969, which was available in 4V versions only in 1969.

This is the 351W-4V V-8 for 1969 with a C9OX experimental cast-aluminum dual-plane intake manifold and Autolite 4300 4V carburetor. 

For one year only (1995), Ford’s Special Vehicle Team (SVT) fitted the Mustang Cobra R with a 300-horse 351-ci (5.8L) V-8, the only year SN-95 Mustangs were fitted with a 351 and only in the SVT Cobra R.

Because the 351W has larger (1/2 inch) head bolts than the 289/302 (7/16 inch), you need bolt spacers, available from Summit Racing Equipment and other aftermarket sources such as ARP, which enable you to install 351W heads on a 289/302 using the 289/302 head bolts.

The 351W “3M” nodular iron crankshaft has larger main and rod journals than the 289/302 along with a longer stroke. This crank had longer connecting rods (5.956 inches) than you find inside the 289/302. For 1969 it was the only 351W4V engine produced with 10.7:1 compression. The  351W-2V engine had a more modest compression ratio of 9.5:1. 

The 351W-4V was equipped with the Autolite 4300 4-barrel carburetor while the 351W-2V was fitted with the Autolite 2100 2-barrel. Ford never produced a high-performance 351W V-8 prior to the Lightning F-150 with the 5.8L High Output V-8. All were fitted with flat-tappet hydraulic camshafts.

Boss 302

Ford’s legendary racebred Boss 302 engine remains one of the most significant high-performance power plants in the company’s history. It was a world beater and symbolic of the end of the classic muscle car era. The Boss 302 engine was introduced just as Ford decided to get out of racing. Think of the Boss 302 engine as a wonderful act of desperation because the 1968 302 Tunnel Port was such a miserable flop for Ford.

In theory, the Tunnel Port cylinder head was a great idea, making a whopping 450 hp at 8,000 rpm. The problem was that racers needed to push it to nearly 9,000 rpm to make checkered-flag power, scattering the engines all over racetracks from coast to coast. Because this problem was epidemic, Ford engineers had to think fast and arrive at a solution everyone could live with to salvage a hard-won reputation for winning.

We will probably never know which came first, the Cleveland engine or the Cleveland cylinder head. But we do know Ford’s engineers took the 351C-4V poly-angle-valve wedge head and used it on the Boss 302-ci engine to achieve peak horsepower in the 6,500- to 7,500-rpm range instead of a rod-snapping 9,000. This was possible thanks to the 351C having the same bore spacing as the 289/302/351W. All it took was cooling passage modifications to these Cleveland castings (because the 351C has a dry intake manifold and the Boss 302 has a wet one), which was easy in production.

Boss 302 engines had 1.73:1 rocker arms mounted on screwin studs with adjustable fulcrums. All had flat-tappet high-performance mechanical camshafts.

The Boss 302 block began life as the 302 Tunnel Port block with a “C8FE” casting number, four-bolt main caps, heavier webbing, forged steel 3.00-inch stroke crankshaft, heavy-duty connecting rods (actually “C3OE” 289 High Performance rod forgings with broached 3/8-inch bolts and beefy shoulders), and TRW forged aluminum “pop-up” pistons designed for Cleveland wedge chambers. Compression was 11.0:1.

Don’t be surprised to find a “C8FE” block in an early 1969 Boss 302 Mustang because quite a few made it into production cars. The rest were surplus castings left over from the Tunnel Port days that made it into the Ford Muscle Parts program and dealer pipelines.

Other Boss 302 features included a dual-advance dual-point distributor that was a Boss 302 exclusive. On top, the Boss 302 had a 780-cfm Holley 4160 4-barrel carburetor. From 1969 through early 1970, Boss 302 engines were fitted with chrome-plated, stamped steel valve-covers. Early in the 1970 model year, Ford went to cast-aluminum valve-covers. Ram-air was not available on the Boss 302 until the 1970 model year. All 1969 Boss 302 Mustangs were non-ram-air. Ignition systems included a dual-point dual-advance/retard Autolite distributor.

351C

There has been a lot of debate through the years as to why Ford produced two engine families displacing 351 ci: the 351W and 335-series 351C. The 351 Cleveland is a small-block V-8 with the attitude of a big-block thanks to very innovative engineering features. The 351C-4V engine does its best work at high RPM thanks to large intake ports and tight wedge chambers offering good quench. This engine suffers from inadequate exhaust scavenging despite its huge intake ports. Exhaust ports tend to be restrictive considering the generous flow going in. You can do some port work on the exhaust side and gain flow, but don’t expect much improvement.

The 351C-4V has never been very productive with low-end torque because its 4-barrel cylinder heads were designed primarily for high-RPM horsepower and not low-RPM torque. This begs the question why Ford put this engine in car lines not intended for high-RPM use, such as Galaxie, LTD, Fairlane, and Torino. The 351C had a brief four-year production life (1970–1974 in North America). It was never practical for Ford to produce two engine families in North America employing the same displacement. The 335-series Cleveland was more costly to produce than the 351W, which sealed its doom as a mainstream engine in North America.

Because the 351C has at least two GM nuances to its architecture, block configuration and poly-angle-valve cylinder heads, it raises questions as to how this engine family was developed in the first place. This has been a point of speculation for many years. The 351C block looks like a Ford/Oldsmobile hybrid with 289/302/351W bore spacing and size coupled with an Oldsmobile V-8’s front-end architecture that includes abundant cast iron and a steel plate timing cover, 12/6 o’clock bolt-pattern fuel pump (the only Ford V-8 to have the 12/6-pattern fuel pump), and a castiron water pump that also resembles Oldsmobile’s. On top, the Cleveland’s poly-angle-valve cylinder heads with those large ports and wedge chambers closely resemble Chevrolet’s 396/402/427/454-ci big-block castings of the era.

Ford’s canted-valve large-port Boss 302 engine arrived in mid-1969 with chrome stamped steel valvecovers, which continued into early 1970 before Ford replaced them with the finned cast-aluminum valvecover shown here.

The Boss 302 was not available with ram-air in 1969. However, the ram-air shaker was available as an option for 1970. 

The all-new 351 Cleveland arrived in 1970 primarily in 4V form with the Autolite 4300 carburetor, though 2V versions were also produced when 351W-2V engines were in short supply. The 4V version was fitted with wedge chamber heads and large ports yielding 11.0:1 compression. The 351C-2V engine was an unplanned 11th-hour undertaking for Ford, arriving with open chambers and smaller intake and exhaust ports for improved low-end torque at 9.5:1 compression. 

This 1973 351C-2V is devoid of the ram-air feature with a Motorcraft 2150 carburetor. What the 351C-2V engine had going for it was better low-end torque than the 4V with larger ports. The 2V’s smaller ports offered better low-end street performance yet fell on its face at high RPM. 

The 351C with ram-air for 1973 was available only with 2-barrel carburetion thanks to tougher federal emissions standards. 

The 1971 Boss 351 and its lower-compression sibling, the 351C High Output for 1972, made the most of the Cleveland’s potential with a hot mechanical flat-tappet camshaft and screw-in, adjustable rocker arm studs. The 351C High Output was available for a short time in 1972 before Ford ended production mid-year.

It is believed that Ford planned for one engine family, the 335-series Cleveland, to cover all engine sizes and to reduce costs. The raised-deck 400-ci Cleveland was introduced in 1971 to replace the 390- and 428-ci FE engines in full-size cars and trucks. In 1975, Ford dropped the 351C low-deck block and destroked the 400 to achieve the 351M. Ford never called the 400 “400M.” Only the 351M is considered the “M” (for Modified or Midland) engine, although it is called “400M” the world over. (Photo Courtesy Tim Meyer)

The 351C is identical to the 351W in terms of bore spacing, size, and bolt patterns. However, the 351C block is a completely different casting designed to take on larger cylinder heads with poly-angle valves, huge wedge and bowl-shaped chambers, and smaller 14-mm spark plugs. The 351C is a higher-revving V-8 thanks to large ports and improved breathing. Also different from the 351W is the thermostat’s block location, instead of on the intake manifold as you find with the 289/302/351W.

From the beginning, 2- and 4- barrel versions of the 351C were produced with 9.5:1 and 11.0:1 compression ratios, respectively. Compression was determined by combustion chamber size. The 2-barrel head has a large open chamber to reduce compression; the 4-barrel head has a wedge chamber. The downside to the 2-barrel head’s open chamber is pinging and detonation issues that make it undesirable. The upside is smaller intake and exhaust ports for improved low-end torque. The best Cleveland factory head comes from Australia with the 4V wedge chamber and 2-barrel intake and exhaust ports, making it the optimum cylinder head for this engine.

The 351C-2V engine is more suited to street performance and low-end torque because it has smaller intake ports for improved velocity. The downside to the 2V cylinder head is large open chambers and poor quench, which makes it susceptible to detonation (pinging). I have never been particularly fond of the 351C-2V cylinder head; however, Tim Meyer of TMeyer Precision Automotive Machining tells me that the 351C-2V head is perfect for street performance if you watch compression and are not planning high-RPM/wide-open throttle operation, which is where detonation takes place.

400/351M

Like the 351C, we will probably never know what led to the 400 Cleveland in 1971 and the 351M in 1975. The 400/351M was a raised-deck (1-inch taller) Cleveland with larger 3.000-inch main journals (which made it taller and wider than the 351C) designed to accommodate the 400’s 4.000-inch stroke.

The 400 debuted for 1971 to replace the 390/428 FE big-block in full-size Fords and Mercurys. For manufacturing cost efficiencies, more than anything else, Ford destroked the 400 to 3.500 inches to achieve the 351M for 1975.

The 400 Cleveland is a “square” engine, meaning it has the same bore and stroke dimensions. The tall-deck 400/351M has 351C-2V heads with huge, open 76.9-cc chambers, which makes them a poor choice for any Cleveland engine project because they lose compression and are prone to pinging and detonation due to poor quench.

Another important issue to remember with the 400 and 351M engines is their bellhousing bolt pattern. Most 351M and 400 blocks have a big-block bellhousing bolt pattern like the 385-series 429/460 engines. However, some were produced with both the big-block and small-block patterns, making them compatible with both types.

Although the 400/351M has a reputation for being a low-emissions slug from the 1970s, it is capable of making incredible amounts of power when fitted with 351C-4V or good aftermarket cylinder heads and induction. And if you’re going to build a 351M, fill it with as much displacement as possible for best results.