Ford Windsor V8 engine
|Manufacturer||Ford Motor Company|
|Also called||Small Block Ford|
|Predecessor||Ford Y-block engine|
|Successor||Ford Modular engine|
|Configuration||90° OHV small-block V8, 4.380" bore spacing|
|Displacement||221 cu in (3.6 L) 255 cu in (4.2 L) 260 cu in (4.3 L) 289 cu in (4.7 L) 302 cu in (4.9 L) 351 cu in (5.8 L)|
|Cylinder bore||4.000" (289, 302, 351W) 3.800" (260) 3.500" (221)|
|Piston stroke||3.500" (351W) 3.000" (302) 2.870" (221, 260, 289)|
|Cylinder block alloy||Cast iron (stock) |
Deck Height: 9.480" ('69-'70 351W ) 9.503" ('71-'96 351W) 8.201"-.210" (BOSS 302) 8.206" (221, 260, 289, 302)
|Cylinder head alloy||Cast iron (stock) A356-T6 (aftermarket)|
|Valvetrain||Cast iron cam, Flat tappet ('62-'84 302, '69-'93 351W) Steel roller cam & lifters ('85-'01 302, '94-'96 351W)|
|Compression ratio||9.0:1 ('87-'92 302)|
|Supercharger||Naturally aspirated (stock)|
|Fuel system||Carbureted (1962-1985) EFI (1980-2001)|
|Oil system||Wet sump (stock) Dry Sump (aftermarket)|
|Cooling system||Jacketed block (stock)|
|Length||27.50" (302, 351W)|
|Width||21.00" (351W) 18.75" (302)|
23.75" (351W) 20.75" (302)
The V8 Ford Windsor motor family is considered by Ford enthusiasts to be one of the greatest and most successful engines produced by the Ford Motor Company. It is referred to as the Small Block Ford by major aftermarket auto parts companies,parts catalogs, on internet forums, and by Ford itself. Introduced in 1962 as part of Ford's "Total Performance" era, the Ford Windsor design succeeded the Ford Y-block engine family, rendering the latter obsolete for performance purposes.
The Windsor family evolved significantly during its 40-year history through technology, performance, and reliability enhancements. Engine displacement also increased from 221 cu in (3.6 L) up to 351 cu in (5.8 L). Engines and their components naturally vary between models and displacements. Despite this, however, many parts are interchangeable. For performance enthusiasts, this means that older motors can frequently be retrofitted with replacement or upgraded parts. An abundant supply of aftermarket parts also exists to fit a wide range of Windsor models.
These motors were originally produced at Ford's Windsor, Ontario engine plant, hence the Windsor designation. From 1969, though, all Ford small blocks (i.e., Windsors) were produced in Cleveland, Ohio. The mid-sized 335 "Cleveland" V8, introduced in 1970, was intended to replace the larger of the Windsor models. The Windsor, however, ended up outliving its replacement.
Ultimately, in 1991, Ford began phasing out the Windsor engine and replacing it with their new 4.6 L Modular V8 engine. In 1996, Ford replaced the 5.0 L (302 cu in) pushrod Windsor V8 with the Modular 4.6 L in the Mustang. Its use continued until 1997 in the F-150 pickup truck, and until 2001 in the Explorer SUV.
From the mid-1970s through the 1990s, the Windsor engine was also marinized for use in smaller recreational boats. As of 2008, Windsor engines, including the 5.8 L (351 cu in) and 5.0L 302, are still being manufactured; available as complete crate motors from Ford Racing and Performance Parts.
The small block Ford engine uses a thin-wall cast iron block with a separate timing chain cover, made from aluminum. This feature differentiates it from later Cleveland, or 351-series engines, that use an integrated timing cover, cast in the block. All Windsors use 2-valve per cylinder heads regardless of whether they are "2V", "4V", or fuel-injected models. The 2V & 4V designations referred to the number of venturi (or barrels) in the carburetor, not valves per cylinder. The valves are in-line and use straight 6-bolt valve covers. Another simple differentiation between the Small Block and "335" Cleveland series is the location of the radiator hose — the Windsor routed coolant through the intake manifold, with the hose protruding horizontally, while the Cleveland had the radiator hose connecting vertically to the engine block. The Cleveland and later "Modified" engines used a canted valve design, allowing for larger valves within the same 4" bore. Something worth noting was the fact that the Ford Engineers designed the Cleveland heads with the same bore spacing and head bolt configuration making it possible (with some light machine work) to bolt Cleveland heads to the Windsor block and in 1969 they did just that creating the Boss 302.
The oil routing in the engine block is unique in that a third passage is drilled parallel to the tappet passages. This passage ensures that oil reaches the main and cam bearings before the tappets, reducing the likelihood of lubricant starvation of the bearings (unlike the 351 Cleveland and the 385 series). The tappets are fed from an inverted 'V' passage cast in the rear under the intake manifold that connects with this passage and is sealed with a steel cap. The third oil passage is visible from the rear of the block with the transmission components removed. It is under and slightly right of the right bank tappet passage. The tappets on the left bank are the farthest from the oil pump and are last to be pressurized by oil upon a dry start. This gives an impression that there is insufficient lubrication, but this is normal and the noise ceases after several seconds of operation.
With the exception of the 289 HiPo, Boss 302 and 351W, all connecting rods use the same 5/16 in. dia. bolts. The rod forgings had undergone some changes throughout its history. The 221, 260 and early 289 (C2OZ-A and C3AE-D) rods used an oil squirt hole to lubricate the piston pin and rings. The oil squirt hole was discontinued in 1964. The same forging continued to be used up to 1967 and all were the same length (5.155 in.). The 302 used a shorter beam (C8OE-A 5.090 in.) but used the same cap up to 1970. In 1971 the cap design was changed from flanged to flat (D1OE-A). This was changed back to the flange design in 1988 due to fatigue failures from increased power output of fuel injection and continued until the end of production. The 289 HiPo and Boss 302 were the same length (5.155 in) used heavier beam and cap forgings and 3/8 in bolts but were machined differently. The former used square head bolts and square cut and the latter were spot faced for 'football head' bolts.
The first engine of this family, introduced for the 1962 model year as an option on the Ford Fairlane and Mercury Meteor, had a displacement of 221 cu in (3.6 L), from a 3.5 in (89 mm) bore and 2.87 in (72.9 mm) stroke, with wedge combustion chambers for excellent breathing. An advanced, compact, thinwall-casting design, it was 24 in wide, 29 in long, and 27.5 in tall (610 mm × 737 mm × 699 mm). It weighed only 470 lb (210 kg) dry despite its cast iron construction, making it one of the lightest and most compact V8 engines of its class. Although all of the 1962 through 1964 221-289 engines used a five-bolt bell housing, the block mount pads varied in length between the 221, and the 260-289 motors requiring different motor mounts to be used.
In stock form it used a two-barrel carburetor and a compression ratio of 8.7:1, allowing the use of regular (rather than premium) gasoline. Valve diameters were 1.59 in (40.4 mm) (intake) and 1.388 in (35.3 mm) (exhaust). Rated power and torque (SAE gross) were 145 hp (108 kW) at 4,400 rpm and 216 lb·ft (293 N·m) at 2,200 rpm.
The 221 was dropped after the 1963 model year.
The second version of the Windsor, introduced during the middle of the 1962 model year, had a larger bore of 3.80 in (96.5 mm), increasing displacement to 260 cu in (4.3 L). Compression ratio was raised fractionally to 8.8:1. The engine was slightly heavier than the 221, at 482 lb (219 kg). Rated power (still SAE gross) rose to 164 hp (122 kW) @ 4400 rpm, with a peak torque of 258 lb·ft (350 N·m) @ 2200 rpm.
In 1962 and 1963 valve diameters remained the same as the 221, but starting in 1964 they were enlarged to 1.67 in. (42.4 mm) (intake) and 1.45 in (36.8 mm) (exhaust). Rated power was not changed.
In 1963 the 260 became the base engine on full-size Ford sedans. Later in the model year its availability was expanded to the Ford Falcon and Mercury Comet. The early "1964½" Ford Mustang also offered the 260, although it was dropped by mid-year, as did the 1964-1966 Sunbeam Tiger Mk I. The 1967 Sunbeam Tiger Mk II used the 289 CID V8 (see 289).
The special rally version of the Falcon and Comet and early AC Cobra sports cars used a high-performance version of the 260 with higher compression, hotter camshaft timing, and a four-barrel carburetor. This engine was rated (SAE gross) 260 hp (194 kW) @ 5800 rpm and 269 lb·ft (365 N·m) @ 4800 rpm.
Ford dropped the 260 after the 1964 model year.
The 289 cu in (4.7 L) Windsor was also introduced in 1963. Bore was expanded to 4.0 in (102 mm), becoming the standard bore for most factory Windsor engines. The 289 weighed 506 lb (230 kg).
In 1963 the 289 was available in two forms: with a two-barrel carburetor and 8.7:1 compression, (SAE gross) rated at 195 hp (145 kW) at 4,400 rpm and 258 lb·ft (350 N·m) at 2,200 rpm. The two-barrel 289 replaced the 260 as the base V8 for full-sized Fords. The second form was the K-code listed below, in 1963 it was available only in the Fairlane.
In 1964 with a four-barrel carburetor and 9.0:1 compression, rated at 210 hp (157 kW) at 4,400 rpm and 300 lb·ft (407 N·m) at 2,800 rpm was available in Mercury Comets.
1964 1/2 (Early 1965) Mustang 289 D-code 4V Engine - The D-code V8 Mustang engine with the Autolite four-barrel carburetor was a rare engine. It was only offered as an option in the 1964 1/2 (Early 1965) Mustangs dated March - September 1964. Some characteristics setting the rare engine apart from other earlier V8s include:
- The air cleaner decal was black, white and red in color (rather than black and orange). It read “289 cubic inch 4-V premium fuel”.
- The timing chain cover had three variations:All D Code engines used an aluminum water pump.
- an oil filler neck;
- a hole for an oil filler neck with a plug in it;
- no oil filler neck or oil filler hole.
- D Code 289’s used an Autolite 4100 4V 1.08 Venturi carburetor.
- D Code 289’s had 5 bolt holes for attaching the bell housing (later engines had 6 bolts).
- Early D Codes utilized a generator and later D Codes utilized an alternator.
Both 1963 and 1964 versions had a five-bolt bell housing pattern that was different from later six-bolt units (Mustangs switched bolt patterns around August 3, 1964).
For 1965 the compression ratio of the base 289 was raised to 9.3:1, increasing power and torque to 200 hp (149 kW) at 4,400 rpm and 282 lb·ft (382 N·m) at 2,400 rpm. The four-barrel version was increased to 10.0:1 compression, and was rated at 225 hp (168 kW) at 4,800 rpm and 305 lb·ft (414 N·m) at 3,200 rpm.
Engine specifications were unchanged for 1966 and 1967. In 1968 the four-barrel 225 hp (168 kW) engine was dropped, leaving only the two-barrel — now reduced back to 195 hp (145 kW).The HiPo 271 H.P. engine was also dropped, making room for the new for 1968 302 V-8. 1968 was the last year of production for the 289 in the U.S.
The 289 was also the engine for the first Australian Ford Falcon GT, the XR Falcon GT.
289 "HiPo" (K-code)
A high-performance version of the 289 engine was introduced late in the 1963 model year as a special order for Ford Fairlanes. The engine is informally known as the "HiPo" or the K-code (after the engine letter used in the VIN of cars so equipped). Oddly, this engine was introduced in 1963 as the only 289 engine available in the intermediate Fairlanes. Lesser powered cars had the 260 engine in that year. Starting in June 1964, it became an option for the Mustang. NOTE: K-code Mercury Comets were the 210 HP 4 bbl carb engine not the High Performance engine as the K-code Fords.
The HiPo engine was engineered to increase performance and high-RPM reliability over standard 289 fare. It had solid lifters with hotter cam timing; 10.5:1 compression; a dual point, centrifugal advance distributor; smaller combustion chamber heads with cast spring cups and screw-in studs; low restriction exhaust manifolds; and a bigger, manual choke 595 CFM carburetor (std 289-4V was 480 CFM). The water pump, fuel pump, and alternator/generator pulley were altered; fewer vanes, extra spring, and larger diameter respectively; to help handle the higher engine speeds. Even the HiPo’s fan was unique. Bottom end improvements included thicker main bearing caps and balancer, larger diameter rod bolts, and a hardness tested and counterweighted crankshaft, all for high-rpm reliability. The HiPo carried SAE gross ratings of 271 hp (202 kW) at 6,000 rpm and 312 lb·ft (423 N·m) at 3,400 rpm.
The HiPo engine was used in modified form by Carroll Shelby for the 1965-1967 Shelby GT350, raising rated power to 306 hp (228 kW) at 6,000 rpm through use of special exhaust headers, an aluminum intake manifold, and a larger carburetor. The Shelby engine also had a larger oil pan with baffles to reduce oil starvation in hard cornering. Shelby also replaced the internal front press-in oil gallery plugs with a screw-in type plug to reduce chances of failure.
From 1966 to 1968, Shelby offered an optional Paxton supercharger for the 289, raising its power (on Shelby GT350s) to around 390 hp (291 kW).
The K-code HiPo engine was an expensive option and its popularity was greatly diminished after the 390 and 428 big-block engines became available in the Mustang and Fairlane lines, which offered similar power (at the expense of greater weight) for far less cost.
In 1968 the small block Ford was stroked to 3.0 in (76.2 mm), giving a total displacement of 302 CI (4,942 cc). The connecting rods were shortened to allow the use of the same pistons as the 289. It replaced the 289 early in the 1968 model year.
The most common form of this engine used a two-barrel carburetor, initially with 9.5:1 compression. It had hydraulic lifters and valves of 1.773 in (45 mm) (intake) and 1.442 in (36.6 mm) (exhaust), and was rated (SAE gross) at 220 hp (164 kW) at 4,600 rpm and 300 lb·ft (407 N·m) at 2,600 rpm. Optional was a four-barrel version rated at 250 hp (186 kW) at 4,800 rpm.
For 1968 only, a special high-performance version of the 302 was offered for the Shelby GT350. Its main features included an angled, high-rise aluminum or iron intake manifold, a larger Holley four-barrel carburetor, and bigger valves of 1.875 in (47.6 mm) intake and 1.6 in (41 mm) exhaust. It had a longer-duration camshaft, still with hydraulic lifters. The block was a high-strength, higher nickel content design made in Mexico. "Hecho en Mexico" casting marks are present in the lifter valley, and its main strength was the appearance of much larger and stronger two-bolt main bearing caps on the engine's bottom end. The heads had special close tolerance pushrod holes to guide the pushrods without rail rocker arms or stamped steel guide plates. The combustion chambers also featured a smaller quench design for a higher compression ratio and enhanced flow characteristics. Additionally, high flow cast exhaust manifolds similar to those on the 289 Hi-Po K-code engine further improved output. Heavy-duty connecting rods with high strength bolts and a nodular iron crankshaft were also included in this package. Rated power (SAE gross) was estimated at 315 hp (235 kW) at 6,000 rpm and 333 lb·ft (451 N·m) at 3,800 rpm. The package, which cost $692 (USD) including some other equipment, was not popular and did not return for 1969. This engine was not a factory engine. Rather, like all Shelby Mustang engines, it was modified by Shelby American in their capacity as a vehicle upfitter. This special engine is well documented in the Ford factory engine repair manual for 1968 Mustangs and Fairlanes. This engine block is considered the strongest production 302 block other than the Boss 302 and the Trans Am 302. The heavy duty Mexican 302 block was produced for several more years, and even showed up on Ford trucks and vans throughout the late 1970s and early 1980s.
Emission regulations saw a progressive reduction in compression ratio for the 302 two-barrel, to 9.0:1 in 1972, reducing SAE gross horsepower to 210 hp (157 kW). In that year U.S. automakers began to quote horsepower in SAE net ratings; the 302 two-barrel carried a net rating of 140 hp (104 kW). By 1975 its power would drop as low as 122 hp (91 kW). Not until fuel injection began to appear in the 1980s would net power ratings rise above 210 hp (157 kW).
Throttle body fuel injection first appeared for the 302 on the Lincoln Continental in 1980, and was made standard on all applications in 1983 except manual transmission equipped Mustangs, Mercury Capris (equipped first with two-barrel (1982), then later 4-barrel carburetor (1983–85)), and also F-series trucks. The block was fitted with revised, taller lifter bosses to accept roller lifters, and a steel camshaft in 1985, and electronic sequential fuel injection was introduced in 1986. While sequential injection was used on the Mustang since 1986, many other vehicles, including trucks continued to use a batch fire fuel injection system. The speed-density based EFI systems used a large, two-piece, cast aluminum manifold. It was fitted on all engines through 1988, after which year it was replaced by a mass-air type measuring system, with the same manifold. The MAF system continued, with minor revisions, until the retirement of the engine in 2001. Ford offered a performance head that was a stock part on 1993 - 1995 Mustang Cobra models and pre- 1997-1/2 Ford Explorers and Mercury Mountaineers equipped with the 5.0 L engine called the GT-40 head (casting id F3ZE-AA). In mid-1997, the Explorer and Mountaineer 5.0 L heads were revised and renamed GT40P. The GT40P heads, unlike the GT40 heads, had a very well developed port shape/design which yielded ~200 cfm on the intake side and ~140 cfm on the exhaust side without increasing the size of the ports at all from standard E7TE castings, and without increasing the exhaust valve size. They also had smaller 59 - 61 cc combustion chambers for added compression, and the combustion chamber shape was revised to put the spark plug tip near the center of the chamber for a more even burn. These GT40P heads are considered by many enthusiasts to be extremely efficient.
The 302 was also offered for marine applications in both standard and reverse rotation setups.
In the 1980s the 302 became more commonly known as the 5.0 Liter, although with its metric displacement (4,942 cc), people dispute whether it rounds to 4.9 L or 5.0L. It is speculated that Ford used the "5.0" moniker to distinguish the 302 from their 300 cu. in. inline Six, which was known as the 4.9. Despite its advertised displacement, Car and Driver referred to the 302 as a 4.9 liter engine.
The 302 remained a mainstay of various Ford cars and trucks through the late 90's, although it was progressively replaced by the 4.6 L Ford Modular engine starting in the early 1990s. The last 302 engine was produced for installation in a production vehicle was at Cleveland Engine Plant #1 in December 2000, as part of a build ahead to supply Ford of Australia, who installed their last such engine in a new vehicle in August 2002. The 302 is still available as a complete crate motor, from Ford Racing and Performance Parts.
In 2001, Ford Australia also built some stroked, 5.6 L (5,605 cc, 342 cu in) Windsors with reworked GT40P heads (featuring larger valves), a unique eight trumpet inlet manifold, long throw crank, H beam rods and roller rockers. They produced 335 hp (250 kW) at 5,250 rpm and 369 lb·ft (500 N·m) at 4,250 rpm. The 5.6 litres of displacement was reached by lengthening the stroke from 76.2 mm (3.0 in) to 86.4 mm (3.4 in).
The Boss 302 was a performance variant of the Windsor, putting what would become Cleveland heads on a special, heavy duty, 4 bolt main Windsor block to improve rated power to 290 hp (216 kW). According to some reports, the canted valve, deep breathing, high revving engine could produce more than 310 hp (231 kW), although as delivered, it was equipped with an electrical rev limiter that restricted maximum engine speed to 6150 rpm. A bulletproof bottom end, thicker cylinder walls, steel screw-in freeze plugs, race prepped crank, special HD connecting rods and Cleveland style forged pistons kept the engine together at high speeds. The key to this engine's power was the large port, large valve, quench chambered, free flowing heads. The Boss 302 Mustang was offered only for the 1969 and 1970 model years. In a January 2010 issue of Hot Rod magazine, a Boss 302 engine built to the exact specifications, settings and conditions to the original engine was tested. It produced a solid 372 hp @ 6,800rpm and 325 lb-ft of torque @ 4,200rpm.
The 351 cu in (5.8 L) Windsor featured a 1.3 in (32.5 mm) taller deck height than the 302, allowing a stroke of 3.5 in (88.9 mm). Although related in general configuration to the 289-302 and sharing the same bell housing, motor mounts and other small parts, the 351W had a unique, tall deck block, larger main bearing caps, thicker, longer connecting rods, and a distinct firing order (1-3-7-2-6-5-4-8 versus the usual 1-5-4-2-6-3-7-8), adding some 25 lb (11 kg) to the engine's dry weight. The distributor is slightly different to accommodate a larger oil pump shaft and larger oil pump. Some years had threaded dipstick tubes. It had a unique head which optimized torque over high-rpm breathing, frequently replaced by enthusiasts with aftermarket heads providing better performance. The early 1969 and 1970 heads had larger valves and ports for better performance. The intake valves and ports were slightly larger on the early engines. The head castings and valve head sizes from 1969 to 1976 were different, notably in passages for air injection and spark plug diameters (1969-1974 18 mm, 1975 and up 14 mm). From 1977 onward, the 351W shared the same head casting as the 302, differing only in bolt hole diameters (7/16 inch for 302, 1/2 inch for 351W). Early blocks (casting id C9OE-6015-B had enough metal on bearing saddles 2, 3, and 4 for four bolt mains) as with all SBF, were superior in strength to most late model, lightweight castings. Generally the 1969 to 1974 blocks are considered to be far superior in strength than the later blocks making these early units some of the strongest and most desirable in the entire SBF engine family including the 335 series. During the 1980s a four barrel version (intake manifold casting id E6TE-9425-B) was re-introduced for use in light trucks and vans. In 1988 fuel-injection replaced the four barrel carburetor. Roller lifters were introduced in this engine in 1994.
The original connecting rod beam (forging id C9OE-A) featured drilled oil squirt bosses to lubricate the piston pin and cylinder bore and rectangular head rod bolts mounted on broached shoulders. There were a number of fatigue failures attributed to the machining of the part and so the bolt head area was spot-faced to retain metal in the critical area, requiring the use of 'football head' bolts. In 1975, The beam forging (D6OE-AA) was updated with more metal in the bolt head area. The oil squirt bosses were drilled for use in export engines, where the quality of accessible lubricants was questionable. The rod cap forging remained the same on both units (part id C9OE-A). In 1982, the design of the Essex V6 engine used a new version of the 351W connecting rod (E2AE-A), the difference between the two parts was that the V6 and V8 units was machined in metric and SAE units respectively. The cap featured a longer boss for balancing than the original design.
The block underwent some changes since its inception. In 1971, The deck height was extended from 9.480 in. to 9.503 in. (casting id D1AE-6015-DA) to lower the compression ratio to reduce NOx emissions without the need to change piston or cylinder head design. In 1974 a boss was added on the front of the right cylinder bank to mount the air injection pump (casting id D4AE-A). In 1974 the oil dipstick tube moved from the timing case to the skirt under the left cylinder bank near the rear of the casting. These details made swapping older blocks from passenger cars with front sump oil pans to more recent rear-sumped Mustang and LTD/Crown Vic Ford cars more difficult unless an oil pan had the dipstick mounted therein. In the 1990s the rear main seal was changed from a two-piece component to a one-piece design and provisions for roller tappets were also added.
Introduced in 1969, it was initially rated (SAE gross) at 250 hp (186 kW) with a two-barrel carburetor or 290 hp (216 kW) with a four-barrel. When Ford switched to net power ratings in 1972 it was rated at 153 to 161 hp (114 to 120 kW), although actual, installed horsepower was only fractionally lower than in 1971.
During the 1990s, motor enthusiasts were modifying 351 Cleveland 2V cylinder heads (by re-routing coolant exit from the block surfaces to the intake manifold surfaces) for use in the 351W resulting in the Clevor (combining Cleveland and Windsor). This modification required the use of custom pistons by reason of differing combustion chamber terrain (canted valves vs. straight valves) and intake manifolds. This combination yielded the horsepower potential of the 351C with the ruggedness of the 351W small block and was possible because more 351C 2V cylinder heads were manufactured than the corresponding engine blocks (the 351M and 400 used the same head as the 351C 2V).
From the late 1960s through the early to mid-1990s the 351 Windsor had a long history of being marinized by Pleasure Craft Marine (PCM) and Indmar for use in Correct Craft and MasterCraft inboard competition ski boats. The early marinized engines were rated at 220 hp (164 kW). Most PCM and Indmar marinized 351’s were rated at 240 hp (179 kW). In the early 1990s, a 260 hp (194 kW) version as well as a "HO" (High Output) version that used GT-40 heads and the Holley 4160 marine carburetor was rated at 285 hp (213 kW). A few 351 GT-40/HO engines were marinized equipped with Throttle Body fuel Injection (TBI) and were rated at 310 hp (231 kW). The marine industry's relationship with the 351W platform ended when Ford was unable or unwilling to compete with GM's mass production of TBI and MPI equipped engines in mass quantity. It was during that time that the recreational marine community's small-block V8 platform of choice shifted to the 350 cu in (5.7L) GM L31 (vortec 5700) engine series.
The Racing Boss 351, not to be confused with the Ford 335 engine Cleveland based Boss 351, is a crate engine from Ford Racing Performance Parts. The block was based on the 351 cu in (5,752 cc) Ford Windsor engine, but uses Cleveland sized 2.75 in (70 mm) main bearing journals. Deck height choices include 9.2 in (234 mm) and 9.5 in (241 mm). Maximum displacements are 4.25 in (108 mm) stroke and 4.125 in (105 mm) bore.
The non cross-drilled block with increased bore capacity became available from the third quarter of 2009. A 427 cu in (6,997 cc) Boss 351-based crate engine producing 535 hp (399 kW) was available from the first quarter of 2010.
In 2010, the MSRP for the Boss 351 block was US$1,999.
In 1980, a very urgent need to meet EPA CAFE standards led to the creation of the 255 cu in (4.2 L) version, essentially a 302 with the cylinder bores debored to 3.68 in (93.5 mm). Rated power (SAE net) was 115-122 hp (86-91 kW), depending on year and application. Cylinder heads used smaller combustion chambers and smaller valves and the intake ports were ovals whereas the others were rectangular. The only externally visible cue was the use of an open runner intake manifold with a stamped steel lifter valley cover attached to its underside, giving the appearance of previous generation engines, such as the Y-Block and the MEL. It was optional in Fox chassis cars including the Mustang and corporate cousin Mercury Capri, Thunderbird, Fairmont, and standard equipment in the Ford LTD. Some variants (i.e. Mercury Grand Marquis) were fitted with a variable venturi carburetor which were capable of highway fuel economy in excess of 27 MPG. Poorly received due to its dismal performance, the 255 was dropped after the 1982 model year.