The Flathead V8 was one of Ford's most important developments. Before the 1932 introduction of this engine (and the accompanying Ford V8 automobile), almost all production cars aimed at average people used straight-4 and straight-6 engines. "Multi-cylinder" engines (like V8s and even V16s) were produced, but were not intended for mass-consumption.

A popular modification for the flathead was conversion to an overhead valve configuration, and many such modification kits were available, including the Ardun heads from Zora Arkus-Duntov who was to go on to fame as the "father of the Corvette". These conversions were not initially demanded by hot rodders looking for extra power, as they had not yet exhausted the capabilities of the flathead configuration, but were demanded by users of the engine in trucks and other such high load applications, where the constant flow of hot exhaust through the block to the exhaust manifolds caused the entire engine to overheat; the overhead valve heads routed the exhuast out more directly, and away from the block.

Both Flatheads were replaced by the Ford Y-block engine soon after its introduction in 1954.

Ford flatheads are still hot rodded today, with a special land speed record class for flathead engines. The current record holder achieves 700 horsepower and 300 miles per hour.

The Flathead was licensed to other constructors; it was used by Simca in France until 1961 for cars and even later on the Simca V8 military truck.

The Flathead was on the Ward's 10 Best Engines of the 20th Century list.

221

The Flathead featured side valves and displaced 221 in³ (3.6 L). The engine block was cast as a single piece for durability. A single-barrel carburetor fed the engine and produced 65 hp (48.5 kW). Later versions of the original 221 produced 75 hp (56 kW) and 85 hp (63 kW). Production of the original flathead 221 lasted from 1932 through 1936.

A similar 221 flathead was used in Ford trucks for 1937 and 1938. Output was 85 hp (63 kW).

A 2-barrel version for 1939 through 1947 produced 85-95 hp (63-71 kW). After the war, Ford continued to use this engine, with power rated at 100 hp (75 kW) for 1949, just as Oldsmobile introduced their Rocket V8.

239

Ford also produced a 239 in³ (3.9 L) version of the flathead from 1939 through 1947 and an updated 239 from then until 1953.

135

A 135 in³ (2.2 L) version was used in Ford trucks from 1937 through 1940. Output was 60 hp (45 kW).

136

A 136 in³ (2.2 L) version was introduced in 1937. Producing 60 hp, the popular engine was used in many Ford vehicles of the era.

255

Ford's final flathead was the 1948-1953 255 in³ (4.2 L) 255. While earlier Ford V8s had the distributor driven directly from the forward end of the camshaft, and so at an inconvenient location for maintenance, this final flathead used a right angle gear drive from the camshaft, placing the distributor atop the engine near the front and so readily accessible. The fuel pump was mounted centrally atop the rear of the engine, driven by a reciprocating pushrod from a lobe on the camshaft.

336

The Lincoln InVincible 8 was a 336 in³ (5.5 L) version of the flathead. It produced 156 hp (116 kW) and was replaced by the Y-block 317 in 1952. Bore and stroke was undersquare at 3.5 in (88.9 mm) by 4.25 in (107.9 mm).