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The Ford 335 engine family were a group of small-block V8 engines built by the Ford Motor Company between 1970 and 1982. The series was nicknamed Cleveland after the Cleveland, Ohio engine plant in which most were cast. The 335 was designed as a mid-sized engine to replace the larger members of the Windsor small-block family as well as the mid-sized FE V8 family. Both of these engine families continued in production, however, with the Cleveland only outliving the FE by a half-decade and eventually abandoned in favor of the more compact Windsor design.


The 335 series was very different internally from the similar-looking Windsor series. The 335 Cleveland used smaller 14 mm spark plugs in one of two different cylinder heads, both with 2 valves per cylinder. The 4V heads had massive valves canted to the sides with a "poly-angle" combustion chamber. A novel feature is the heads are not straight — they are horizontal in front and angled in the rear with an integrated twist. These covers are secured with 8 bolts, as opposed to 6 on the Windsor.

A simple differentiator between the Windsor and 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 a dry manifold with the radiator hose connecting vertically to a separate timing chain cover.

351 Cleveland

351 Cleveland engines
Code Engine type Years Compression Notes
H 351C-2V 1970-1974 Low
M 351C-4V 1970-1971 High
R 351C-4V "Boss 351" 1971 High Very rare, solid lifters
R 351C-4V HO 1972 Low Very rare, solid lifters
Q 351C-4V "Cobra-Jet" May 1971-1973 Low Rare
See also the Cleveland-derived Boss 351 and quite different 351 "Windsor"

The 351 Cleveland was introduced in 1970 as Ford's new muscle car engine and was built through the end of the 1974 model year. It incorporated elements learned on the 385 big-block series and the Boss 302, particularly the poly-angle combustion chambers with canted valves and the thin-wall casting technology.

Both a 4V (4-barrel carburetor) performance version and a 2V (2-barrel carburetor) basic version were built, both with 2 valves per cylinder. The latter had a different cylinder head with smaller valves, smaller ports, and open combustion chambers to suit its intended applications.

Only the Q-code 351 "Cobra Jet" (1971-1973), R-code "Boss" 351 (1971), and R-code 351 "HO" (1972) versions have 4-bolt mains although all 335 series engines (351C/351M/400M) have space for them even in 2-bolt main form. The main difference between 351W/351C/351M/400M engines is connecting rod length and main bearing size. The 351/400M engines have the largest bearing size and the tallest deck height while sharing the 429/460 bell housing pattern. The 351C engine has a medium main bearing size and shorter connecting rods than the 351W and the 351/400M while retaining the SBF bellhousing pattern. The 400M engine has the longest stroke of any SBF or 335 series engine.

All of the 351C and 351/400M engines differ from the 302/351W by having an integrated timing cover casting in the front of the block to which the radiator hose connects.


The majority of 351 Cleveland engines are H-code 2V (2-venturi carburettor) versions with low compression. These were produced from 1970 through 1974 and were used on a variety of Ford models from compact to intermediate.


The M-code version was produced from 1970 through 1971. It used a high 10.7:1 compression ratio with "4V" quad-barrel carburetors and the quench head-design 4V heads. Hydraulic lifters were also specified, with the M-code producing about 300 hp (224 kW). 2-bolt main caps were used along with a cheaper cast iron intake manifold.

1971 R-code (Boss 351)

See also Ford Boss 351 engine

The 1971 R-code "Boss 351" used higher compression (11.7:1) with the quench head 4V heads, solid lifters, an aluminum intake manifold, and 4-bolt main caps. It produced about 330 hp (246 kW).

1972 R-code

The R-code 351 Cleveland for 1972 was somewhat different. It reduced compression for emissions compliance and used open-chamber heads, although the solid lifters were retained. It produced 277 hp (207 kW) using the new SAE net system.

Q-code (Cobra-Jet)

The Q-code "351 Cobra Jet" version was produced from May 1971 through the end of 1973. It was a low-compression version of the 4V design with the cheaper cast-iron intake manifold but included a special camshaft, dual-point distributor, and 4-bolt main bearing caps. 266 hp (198 kW) (SAE net) was recorded for 1972 which fell to 246 hp (183 kW) for 1973.

302 Cleveland

Note that there was also a 302 "Windsor"

This engine was built only in Australia, and was intended to give their consumers a five liter alternative to the 351 Cleveland as the Ford "Windsor" series of engines was not commonly available there. Utilizing a locally produced 351 Cleveland block, 302 in³ (4.9 L) was attained by reducing the stroke of the 351C from 3.5 to 3 inches (89 to 76 mm). Additionally, the 302C cylinder heads were designed locally, with smaller combustion chamber to compensate for the reduced stroke of the engine.

This combination of closed combustion chambered quench heads with smaller 2 barrel style ports made a more powerful setup known in the USA as "Australian heads". These heads interchange directly onto 351C engines, and are highly sought outside of Australia as a low-cost method to increase compression ratio. They are a good street alternative to the over ported 4 barrel heads. Using the 302C cylinder heads on an otherwise unmodified 351C will increase the compression ratio beyond a safe level for regular pump fuel. Using the small chamber 302C cylinder heads properly requires engine design changes (deck clearance, piston design, cam shaft specifications) optimized for the intended use.


The big-block FE engine family was getting rather tired and outdated, and the 385 family could not meet the efficiency requirements of the time. At the same time, the small-block Windsor engines were too small and high-revving for Ford's fullsize car and truck applications. So the company went to work on a new small-block to meet the desired levels of economy while still providing the kind of big-block torque that was needed to move 2+ ton vehicles.

The Ford 400 engine had "square" proportions, with a 4.0 in (102 mm) bore and stroke; it therefore displaced 402 in³ (6.6 L), making it the largest small-block V8 made at that time. It was introduced in model year 1971 with a full half-inch (12.7 mm) longer stroke than the 351 Cleveland, making it the longest-stroke Ford pushrod V8 engine. A long-stroke engine has good low-end torque, for which it trades high-end power. This was a good compromise given Ford's requirement for an engine to power heavier mid-size and full-size cars and light trucks. The M-block, as it became known, was the last pushrod V8 block designed by Ford, and it had a deck height over an inch (25 mm) higher than the Cleveland. The M-block does share one element with the Windsor family: it has large 3.00 inch main journals.<ref>Template:Citation/core{{#if:2006|}}</ref>

The 400 was seen as a smaller and lighter replacement for the big Ford 385 engines, the 429 and 460, in Ford's big cars. Weighing just 80% of a similar big block, it was originally available in Ford's Custom, Galaxie and LTD lines, and in Mercury's Monterey, Marquis, and Brougham. Later, it would power the Ford Thunderbird, the Lincoln Continental, and Mark V.

The vast majority of 400 blocks use the same bellhousing bolt pattern as the 385 family big-block to make it compatible with the higher torque-capacity C6 transmission used on the large cars and trucks. There were a small number of 400 block castings that use a "small block" pattern on the rear for mounting an FMX transmission. These castings are rare. The 400 was modified in 1975 to use unleaded gasoline.

351 Modified

Engine dimensions
351M/400 351C
Nominal main bearing size 3.000 in (76.2 mm) 2.7149 in (69.0 mm)
Rod length 6.58 in (167.1 mm) 5.78 in (146.8 mm)
Deck height 10.297 in (261.5 mm) 9.206 in (233.8 mm)

When the 351 Cleveland was withdrawn after the end of the 1974 model year, Ford needed another engine in the 351 cubic inch (5.8 L) class, since production of the 351 Windsor was not sufficient and the 390 FE was being retired as well. To replace the 390, Ford took the 400 engine's tall-deck block and de-stroked it, with a shorter throw crankshaft borrowed from the 351 Windsor, and taller pistons, to produce a 351 cubic inch (5.8 L) engine whose components were largely compatible with the 400. This engine was called the 351M and as a back-formation the taller-deck block became known as the M-block. These engines were built in Cleveland, and the performance reputation of the 351 Cleveland engine was such that the company continued to refer to "351 Cleveland" in marketing for a couple years after the change.

Light truck usage

For the 1977 model year, Ford decided to replace its ageing FE big-block 360 and 390 engines in its light truck line with its new 351M and 400 engines. For light truck use, beefed-up blocks were designed. These enhancements were added to all M-block engines starting with the 1978 model year.

Replacement in cars

1979 was the final year the M-block engines were used in cars. After that, the Ford 351 Windsor at 5.8 L was the only large car engine used. Reduced demand for large engines due to fuel economy regulations led to the abandonment of the Cleveland production line that produced the 351M and 400 engines.

Replacement in trucks

The M-block engine was designed when first-generation pollution controls were already in place in the United States, and the engine was designed to support the Thermactor air injection reaction (AIR) and exhaust gas recirculation (EGR) systems internally inside the block and heads. Previous engine designs required bulky and unsightly external tubing to feed Thermactor air into the exhaust manifolds and exhaust gas to the EGR valve below the carburetor, but this was all built in to the M-block engine.

This all made adapting the M-block to the second generation of emissions control equipment harder. One requirement of the second-generation equipment was an O2 sensor in the exhaust, which had to be placed before the Thermactor air was added. Since Thermactor air was injected right into the block's exhaust ports in the M-block, there was nowhere for the O2 sensor to go.

It would have been possible to alter the M-block to work, but it would have required significant effort. Ford decided to simply scrap the M-block engines and replace them with updated 351 Windsor engines at the small end, and a combination of the 6.9 L Navistar diesel and the 460 at the top end. 1982 was the last year the M-block was sold.

See also

External links