Among the many high-performance American V8 engines developed in the 1950s and 1960s, Ford’s 335 series had the potential to be one of the greatest.
Better known as the Cleveland after the factory in Ohio where most examples were built, it could be persuaded to produce formidable power outputs despite its relatively modest size as in the Boss 351 Mustang (pictured).
Here we take a look at the Cleveland and investigate why, through no fault of its own, it could never fulfil its early promise.
(Note: power figures have been supplied by Ford’s archive department. The US method of measuring power changed in 1972, so outputs of earlier cars will seem disproportionately high.)
The Cleveland was largely based on the mid-size V8 informally known as the Windsor, built in Ontario, Canada for use in cars dating back to the 1962 Ford Fairlane. The Cleveland, pictured above with Ford receptionist Pat Thornberry, was outwardly similar, but its cylinder block enclosed the timing gear and was therefore longer and heavier.
On the plus side, the Cleveland had a superior cylinder head design – or, in fact, two. Heads were referred to as 2V or 4V according to whether they were intended for engines with two or four carburetor venturis. Both were notable for their excellent airflow.
Ford’s official name for the family was chosen because the minimum expected capacity of the engines was 335 cubic inches (5.5 liters).
As things turned out, that size was never used. Most Clevelands were larger, and one version never sold in the US was smaller.
The Cleveland heads were available to the public before the rest of the engine was. In 1969, they were fitted to the high-revving Boss 302 Mustang, where they sat on top of a 302ci (4.9-liter) Windsor block.
Ford quoted a power output of 290 horsepower, though this is widely believed to be an underestimate. The company never again fitted the more free-flowing heads to the lighter block, but it’s interesting to speculate what wonders could have been achieved if it had.
Entire Cleveland engines went on the market in the 1970 model year in two forms. Both had a 4.0-inch (101.6mm) bore and a 3.5-inch (88.9mm) stroke for a total capacity of 351 cubic inches (5.8 liters), but the 351C H-Code, with its 2V heads and mild 9.5:1 compression ratio was the more leisurely of the two, with a power output of 250bhp matching that of the 351ci Windsor.
In this form, the Cleveland was used for cars whose customers preferred power in the middle of the rev range rather than the top. Examples included the Falcon, the Fairlane and the Torino (pictured).
The 351C M-Code was the more powerful of the early engines. Identical to the H-Code in all dimensions, it had the 4V heads and a carburettor to match, a higher compression ratio of 11.0:1 and different pistons. For these and other reasons, the power output as measured in those days was 20% higher at 300 BHP.
Sportier versions of the Torino were sold with this engine, as were the Mustang and the Mercury Cougar (pictured). Owners of all cars powered by the H-Code were advised to use only premium fuel.
Boss 351 Mustang
The Cleveland reached its peak as early as 1971. A new derivative called the R-Code was produced and fitted only to the Boss 351 Mustang.
If the previous year’s M-Code had seemed impressive, the R-Code showed what Ford’s engineers could really do. Maximum power was officially 330 BHP, a figure no standard Cleveland-engined car would ever achieve again.
By this time, American manufacturers were increasingly having to prioritise fuel economy and exhaust emissions over performance. The brilliant cylinder head design which had been the Cleveland’s best feature would now have to be made ineffective.
Despite its exciting name, Cobra-Jet, the 4V engine launched in 1971, was an M-Code hampered by a lower compression ratio of 10.7:1, among other restrictions. Maximum power was 280 BHP, short of what the M-Code had produced but a good effort in the circumstances. By the end of 1972, the Cobra-Jet, or Q-Code, had completely replaced the M-Code.
De Tomaso Pantera
Unlike the Windsor, the Cleveland engine almost never appeared in anything not branded Ford or Mercury, but in Q-Code form it did power most versions of the De Tomaso Pantera from 1971, when Ford bought a controlling stake in the Italian company.
Much more successful and better regarded than the Windsor-powered Mangusta it replaced, the Pantera remained in production until the early 1990s.
No longer the Boss
The R-Code as fitted to the ’71 Mustang was no longer acceptable by 1972. A low-compression (8.6:1) version was devised with a power output of just 266 BHP, 64 BHP less than that of the previous year’s Boss 351.
The new and significantly slower car was known as the 351HO. A disappointed journalist is reported to have said, “Ford hasn’t dropped the Boss part for nothing.”
The largest engine in the Cleveland family had bore and stroke measurements of 4.0 inches, giving a capacity of 402ci (6.6 liters). Ford rounded this number down to the nearest hundred to give the engine its official name, 400.
To accommodate the longer stroke, the cylinder block had to be taller than that of the 351C. The extra metal increased the engine’s weight and center of gravity, though these were not major problems for cars like the 1972 Ford LTD (pictured) fitted with the 400.
The 400 was never intended to be a high-power engine. It only ever had the 2V cylinder heads and was designed to perform well at moderate engine speeds.
The original power output of 260 BHP was the highest ever available. Owners of, for example, the Ford Thunderbird (pictured) would not have been interested in having anything racier under the hood, though they might have preferred more than the 153 BHP which was standard for the engine in its later years.
Decline of the 351C
Amazing as it would no doubt have seemed just five years earlier, the 351C engine lasted only until 1974, when it was fitted to, for example, the Ford Ranchero pickup (pictured).
The potential of the Cleveland cylinder heads was now being suppressed by increasingly low compression ratios, among other attempts to improve fuel economy and exhaust emissions. The lowest output of the engine before it was abandoned was just 162 BHP in some versions of the Torino.
The 351C was replaced for the 1975 model year by the 351M, which had the same bore (4.0 inches), stroke (3.5 inches) and capacity (351ci/5.8 liters) but was based on the taller and heavier block of the 400. This saved Ford the trouble and expense of manufacturing two blocks for the same engine family.
The 351M was used in passenger cars until 1979 (Mercury Cougar pictured above) and in trucks for three years after that. By the end, power outputs were down to 132 BHP, an amazingly low figure considering the strength of the related engine in the 351 Boss Mustang a decade earlier.
In 1971, Ford Australia began building Cleveland engines in its Geelong factory, and developed the smallest version yet (with a 3.0-inch bore and a 302ci/4.9-liter capacity) for its own use.
The Australian engines appeared in several versions of the Falcon and, when supplies from the US ran out, in the De Tomaso Mangusta. Geelong also built special 351C cylinder blocks which were sent to America and used as the basis for NASCAR race engines long after the 351C had gone out of production in the US.
The home of the Cleveland V8 was the now closed Cleveland engine plant number 2 at Brooke Park in Ohio. It built its last engine, a 3.0-liter V6, in 2012, and its employees moved to engine plant number 1, which had, ironically, built later versions of the Windsor V8 for many years, and is now the closest thing to the Cleveland’s spiritual home.
In 2016, Ford invested $145 million into plant number 1 so that it could produce the 3.5-liter EcoBoost V6 engine, which powers everything from the GT supercar to the F-150 pickup in various outputs.