Oldsmobile overhead valve V-8 engine GM

Few things remade the American auto industry more fundamentally or quickly than the introduction of the overhead valve V-8 engine in 1949. The radical new design, which allowed automakers to offer smaller, more efficient and powerful engines than ever before, while improving economy and durability, completely displaced the flat-head engine within a decade.

The revolutionary new design, created simultaneously by Oldsmobile and Cadillac, traded side-mounted poppet valves within the cylinder block in favor of valves located inside the cylinder head and activated by pushrods. Although the design dates to the dawn of the automotive age—Rudolph Diesel developed a prototype in 1893, and Buick Manufacturing Co. patented the design in 1902—American automakers favored the simpler and cheaper flathead engines through the end of World War II.

The transition from old school to new started shortly after the war, and within a decade flathead engines had given way to powerful V8s with overhead valves and names like the Nailhead and the Red Ram and the Rocket. By 1955, nearly every American automaker offered an OHV engine. Those that couldn’t keep up, including Hudson, Nash, and Packard, didn’t last long.

Oldsmobile Rocket 88/98

General Motors, which remains the world’s largest producer of pushrod OHV engines, started the revolution when Oldsmobile and Cadillac began developing their OHV engines in 1945. We’ll start with Olds and return to Caddy in another article.

With few exceptions, flathead engines—also known as side valve engines—dominated the American automotive landscape. This “L-head” design dates to the earliest days of the motorcar, placing the valves alongside the cylinder within the block. It’s a simple design with few parts and excellent reliability, but it also suffers from low efficiency and power because air must follow a serpentine route to the combustion chamber. The engines also provide very low compression—just 5:1 in Ford’s famed 3.6-liter flathead V-8.

As in America, over in Europe manufacturers were experimenting with a range of engines and technologies, including monoblocks, overhead cams, steam, and diesel engines. Bugatti produced a number of overhead cam iterations of their straight-eight cylinder engines, while American manufacturer Duesenberg created their own exotic straight-eight overhead cam engines considered to be some of the best engineering of the century. By 1929 Cadillac had an equally impressive V-16 overhead valve engine, basically two of their straight-eights running independent of each other with a common crank. But flatheads were the most economical and most simple to manufacture for mass production.

After WWII, straight-eight and 12-cylinder engines were considered “luxury” or “upscale” powerplants. Despite the expense of 12-cylinders and the drawbacks of straight-eights, Detroit still needed to sell them along with four- and six-cylinder engines. Straight-eights created a certain amount of crankshaft “whip,” which affected timing and durability. They took up a lot of room—both lengthwise and height wise—and weight was a problem. Comparatively, the overhead-valve V-8 configuration eliminated crankshaft twist and was inherently lighter and easier to package, which became critical as styling evolved and dictated longer, lower, and wider proportions. “Oversquare” design—where the stroke is shorter than the bore—added to shorter deck heights, leading to lower profiles and stronger piston rods with less flex.

A young draftsman named Gilbert Burrell led Oldsmobile’s development of the engine, which started in 1945. Turns out Cadillac had launched a similar project, and, eager to defend its position as GM’s most innovative brand, lobbied heavily to have the Olds project killed. That led to something of an internal fight, which Oldsmobile won when it petitioned GM president “Engine” Charlie Wilson, to continue developing its Rocket V-8.

Oldsmobile won that fight and continued working on a 287-cubic-inch engine. The low octane gasoline of the era often limited compression ratio of flathead engines to avoid the risk of pre-ignition. The oversquare nature of an overhead valve engine allowed engineers to develop engines with shorter strokes and larger bores, reducing friction and engine speed—and the risk of pre-ignition. Putting the valves in the cylinder head improved airflow and moved more air through the combustion chamber, allowing engineers to increase displacement, and therefore power. Oldsmobile soon developed a 303-cu-in engine with a 7.5:1 compression ratio and 135 horsepower, a significant increase over its best flathead engine.

In 1949, Oldsmobile introduced the Rocket in the 98 and, two months later, in the smaller, lighter 88. The Oldsmobile 88 offered superlative performance, which attracted younger buyers and won praise from the growing number of automotive magazines. No less impressive, it inspired the hit song Rocket 88, widely considered the first rock and roll tune.

The Rocket’s small size and big power helped Oldsmobile dominate auto racing. Robert “Red” Byron won the NASCAR strictly stock class in an Oldsmobile 88 in ’49, and Olds-powered cars won five of the eight Grand National races. The car saw even more success in 1950, taking more than half of all wins with legendary drivers like Curtis Turner, Dick Linder, and Ed “Fireball” Roberts Jr. Other automakers started seeing some success with overhead valve engines by 1952, but Oldsmobile remained dominant for several years.

Given the Rocket’s success, it didn’t take long for hot rodders to embrace overhead valves. A bone-stock Rocket easily out-performed even a highly modified Ford flathead V-8, and a growing aftermarket of go-fast parts made the Rocket, well, a rocket. That made them formidable drag racing engines. Arnie “The Farmer” Beswick drove his 303-cu-in-powered Olds to victory in the 1955 and ’56 NHRA Nationals. Olds dominated the B/Stock and gasser classes well into the ’60s, with countless racers copying the formula (pioneered by “Big” John Mazmanian and Stone, Woods, and Cook) of stuffing a supercharged Rocket into a Willys coupe.

Oldsmobile continued developing the Rocket, increasing the displacement and compression ratios over the years to boost power. The engine grew to 324 cubic inches and a compression ratio of 8.5:1 by 1956, a combination good for 240 horsepower.

By 1957, nearly every American automaker offered an overhead valve V-8. Oldsmobile responded with the J-2 Golden Rocket, a high-performance version with a trio of two-barrel carburetors and a compression ratio of 10.0:1. It made 312 horsepower. For comparison, 1957 Chrysler 300 Hemis produced 375 hp, but in a much heavier package, while Ford’s high performance 312-cu-in Y-block yielded 270 hp. Cadillac’s 364-cu-in V-8 netted 275 hp, so combining the Rocket 88’s lighter weight and lower displacement placed Olds at the top of performance efficiency and power. Olds discontinued the J-2 two years later when it introduced a Rocket with 394 cubes.

Oldsmobile continued producing the venerable Rocket through 1964 in a variety of configurations that made anywhere from 250 horsepower to the 345-horse hammer found in the 1964 Jetstar. The following year, Olds introduced a redesigned V-8 with a forged crankshaft, longer stroke, and other performance improvements.

By that time, the OHV revolution was complete and the flathead engine was a quaint memory.