To name the most influential American car of the postwar era might be an impossible task, but here’s one blue-ribbon candidate: The 1949 Oldsmobile.

Some automotive pundits like to say the 1949 Oldsmobile 88 was America’s first muscle car, but we think that misses the mark. In 1949, the term “muscle car” didn’t yet exist. No one would have known what you were talking about. The real muscle car era as we know it, and as it came to be understood, begins in 1964.

Besides, the ’49 Olds played a far more important and fundamental role in the Motor City’s historical timeline: Essentially, it defined the popular postwar automobile. The Olds offered, in one package, a modern, fully automatic transmission and an overhead-valve, high-compression, short stroke V8, two features that in a few short years, all American cars would be expected to share. Indeed, in the American market, any popular-priced vehicle without these these two key elements was practically a niche product.

Formally announced in January of 1949, a few months after the Cadillac OHV V8, its General Motors stablemate, the Oldsmobile Rocket V8 was first offered in the luxury 98 series, then in the mid-priced, A-Body 88 series shortly thereafter (launching the famous “Rocket 88” of song and story). While both the Cadillac and Olds overhead-valve V8s were based on the groundwork of GM’s research division and its illustrious vice president, Charles “Boss” Kettering, the two engines are individual designs and share no common components. The example above, naturally enough, is shown mated to a Hydra-Matic four-speed automatic transmission.

Displacing 303 cubic inches, the Rocket boasted oversquare proportions with a bore of 3.75 inches and a stroke of 3.4375 inches. This advanced short-stoke layout offered dramatically lower piston speeds, reducing friction and wear, while the overhead-valve cylinder heads provided improved breathing and a more compact combustion chamber, enabling a greater compression ratio—the key to increased efficiency.

While the Rocket V8 was initially produced with a compression ratio of 7.25:1, only a quarter-point higher than the venerable Olds L-head six before it, the specs are misleading. The L-head was staggering to the end of its production life, fully optimized, while the V8 was at the base of its development curve, bursting with potential. Originally rated at 135 hp, the first-gen Olds V8 would eventually grow to 394 CID and 345 hp in 1964, using compression ratios as great as 10.5:1.

So great was Kettering’s contribution to the Olds V8 that at one point, the division initially planned to name the engine after him, as shown on the prototype valve cover above. However, the product naming conflicted with GM corporate policy, so the engine plant in Lansing was named in his honor instead, and the name Rocket was adopted for the engine. Kettering gets the credit for recognizing that petroleum industry advances during World War II would make high-octane gasoline available to the public in vast quantities, supporting higher compression ratios and far greater power and efficiency. In one of his test programs, a GM sedan with 12:1 compression ratio delivered 36 miles per gallon at a steady 50 mph, running on 100 octane gasoline—an improvement in fuel economy of nearly double.

As part of its marketing campaign for the Rocket V8, Oldsmobile arranged for an 88 convertible to handle the pace car duties at the Indy 500, with speedway president Wilbur Shaw at the wheel. Note the stylized rocket chrome trim on the front fender. As part of the festivities, on race day the Purdue University Marching Band spelled out the word “OLDS” in formation on the front stretch.

Actually, Oldsmobile continued to offer the old L-head six, now rated at 105 hp, in the bottom-of-the-line 76 series in 1949-50, but it’s difficult to tell if many even noticed. The Olds Rocket reset the bar for American sedans in the low-to-mid priced field, and by 1955 every U.S. manufacturer offered an up-to-date overhead-valve V8 in its lineup.