In the 1920s, moonshine runners upgraded their vehicles to outrun authorities, eventually leading to organized events in the early 1930s. Bill France Sr. formed NASCAR in 1948 to unify rules, requiring cars to be made of parts available to the public and have sold over 500 units. The 1949 Oldsmobile Rocket V-8 was widely recognized as the first postwar modern overhead valve engine available to the public, and the motto became "win on Sunday, sell on Monday." However, the Hudson Hornet, with its inline six-cylinder engine, won in 1951, 1952, and 1953, proving that engine power wasn’t the only factor.
In 1957, the Automobile Manufacturers Association banned manufacturers from using race wins in advertising and directly supporting race teams. The desire for higher performance cars led to limited production “special edition” cars, and manufacturers began producing larger engines to remain competitive. In 1963, NASCAR restricted engines to a maximum displacement of 7.0 liters and two valves per cylinder. Ford sold enough of their aerodynamic Galaxies to qualify as stock, and they dominated the 1963 season.
By 1965, Ford adapted two single-overhead-cams to their 427 V8, but NASCAR changed the rules to require a single cam-in-block. In 1966, Chrysler sold enough 426 Hemis to compete again, debuting in the Dodge Charger. Richard Petty dominated 1967, winning 27 of 48 races in a Plymouth Belvedere. The 1969 Torino Cobra, later renamed the Talladega, featured aerodynamic improvements, and Ford won six straight Manufacturer Championships. David Pearson set a new NASCAR record in 1970, exceeding 190 mph (310 km/h) qualifying at Daytona in a Ford Torino Cobra.
The 1970 Homologation rules were changed to require one car for every two U.S. dealers to be built for sale to the public, hoping to delay the use of aero-bodies. NASCAR restricted aero-cars to a maximum engine displacement of 305 cu in (5.0 L) in 1971. In 1972, R.J. Reynolds became the major sponsor of NASCAR racing, significantly increasing financial contributions. The 1973 oil crisis meant that large displacement special edition homologation cars of all makes were suddenly sitting unsold.
A stock car originally meant an automobile that had not been modified from its factory configuration. Today, most American stock cars are silhouette cars, purpose-built racing machines built to a strict set of regulations. Other forms include "street) stock", "pure stock", "hobby stock", "showroom stock", or "U-car" racing, as well as modifieds and late models. Late models vary from region to region, with different sanctioning bodies maintaining their own rule books.
NASCAR is the largest stock car racing governing body in the world, with three national championship touring series: the NASCAR Cup Series, the NASCAR O'Reilly Auto Parts Series, and the NASCAR Craftsman Truck Series. The Daytona 500 is the most famous event in the Cup Series. The Automobile Racing Club of America (ARCA) was founded in 1953 and was purchased by NASCAR in 2018. Other national or regional sanctioning bodies include the American Speed Association (ASA), Champion Racing Association (CRA), and International Motor Contest Association (IMCA).
Internationally, stock car racing has not enjoyed the same success as in the United States and Canada. Brazil has a successful stock car series, while Argentina’s Turismo Carretera also features stock car competitions. Stock car racing in the NASCAR mould (AUSCAR) had a following in Australia, but was overtaken by the Supercars Championship. In the United Kingdom, the term 'stock cars' refers to a specialized form of racing that bears little resemblance to any road car. Canada has a growing stock car racing scene, with vehicle models from Chevrolet, Dodge, and Ford.
Stock car races take place predominantly on oval tracks of 3 or 4 turns, with all turns to the left. Oval tracks are classified as short track (less than 1 mile), intermediate or speedway (1 to 2 miles) or superspeedway (over 2 miles). Road courses are also used.
Minor car-to-car contact is generally accepted in stock car racing. Drafting is used on intermediate tracks and superspeedways to reduce drag, a tactic “discovered” by Junior Johnson during his winning performance at the 1960 Daytona 500.