Buick XP-300

The XP-300, which was initially designated the XP-9,[1][2] was designed by General Motors (GM) vice president of engineering Charles Chayne,[2][3] along with Ned F. Nickles.[1] Chayne had previously assisted Harley Earl in designing the 1938-39 Buick Y-Job, often regarded as the first concept car.[1] In May 1951, Chayne granted approval for construction of the XP-300 along with a counterpart GM concept car, the Le Sabre.[1][2]

The XP-300 features a wraparound windshield, three tailfins, and a grille that resembles an electric razor.[1] It also includes push-button power windows and seats.[1] Although somewhat similar in appearance to the Le Sabre, the XP-300's styling was noticeably cleaner than the more futuristic, rocket-inspired lines of its counterpart.[1] Furthermore, while the Le Sabre generally reflected Earl's design philosophy, the XP-300 was more in line with Chayne's conception of the future of Buick production cars, and its front end design ultimately foreshadowed the 1954 Buick line.[1] The car's name reflects the fact that it produced over 300 horsepower (220 kW) and was an experimental (XP) vehicle in nature.[3]

Buick XP-300 interior

The XP-300's body and frame were welded together into a single unit.[1][3][4] It shares many common mechanical components with the Le Sabre.[1] Representative of GM's "long and low" design philosophy in the 1950s, the XP-300 measures over 16 feet (4,900 mm) in total length and has a 116-inch (2,900 mm) wheelbase with just 6.5 inches (170 mm) of ground clearance.[1][3][5] The car is only 39.1 inches (990 mm) in height and 80 inches (2,000 mm) in width.[6] Weighing in at 3,125 pounds (1,417 kg),[4] the total weight of the car was reduced by its use of heat-treated, aluminum body panels.[1][3]

The car also features relatively heavy and wide drum brakes that necessitated two sets of brake shoes for each wheel.[1][3] In addition, it boasts hydraulic steel bars that made it more rigid while being driven, helping form a framework somewhat similar to a roll cage;[1][4] similarly, four hydraulic jacks that could raise either the driver or passenger side of the car facilitated easier tire changes.[1][7] The XP-300 also has de Dion axles based on a Daimler-Benz design used for Grand Prix race cars.[8] It additionally features four coil springs and a hydraulic system more complex than that of the Le Sabre, which operates the car's cowl vents, door-locking devices, hood, jacks, seats, and windows.[9]

The car was painted "Venus White".[9] It has functional chrome louvers running down its rocker panels; the forward-mounted louvers served to vent heat from the engine, while the aft ones allowed air to enter the passenger compartment.[10][9] Similarly, a chrome fin runs through the center of the car's trunk, hiding hinges for the twin deck lids, while a floodlight-style, sealed-beam backup lamp was mounted in the central fixture, which imitates the exhaust of a jet engine.[9] The car was originally built with both a folding convertible top and a hardtop that were interchangeable, although the hardware to mount the latter has been removed and the hardtop can no longer be used.[9]

The interior of the XP-300 features pleated blue-leather bucket seats with adjustable inflatable air bladders and a center console.[9] The car also has a telescoping steering wheel and an instrument panel displaying a prominently mounted combined speedometer/tachometer as well as a fuel gauge.[9] It also boasted numerous technologies considered safety features in 1951, including its dual brakes, adjustable seats, and adjustable steering wheel in addition to seat belts.[6][10]

The XP-300 was powered by a supercharged V8 engine made of aluminum that weighed just 550 pounds (250 kg) yet produced 335 horsepower (250 kW).[1][11] This engine is 250 pounds (110 kg) lighter than the engine used in the contemporary production Buick Roadmaster, but is twice as powerful.[7] The XP-300's engine could run on either gasoline or methanol, and the car featured two separate fuel fillers and fuel tanks, one for each fuel.[12] The engine was fitted with a Bendix-Eclipse two-barrel carburetor,[12] with one using gasoline and the other methanol.[7] The methanol carburetor automatically cut in once the gasoline carburetor reached 40% throttle,[7] in order to prevent engine knocking during rapid acceleration.[6]

With a displacement of just 215.7 cubic inches (3.535 L), the engine, which also powered the Le Sabre, had an impressive power-to-size ratio for the era.[13] It also boasted a chain-driven camshaft and hemispherical combustion chambers,[13] the latter of which allowed it to achieve an air-to-fuel-mixture ratio of 10.0:1, also considerable for 1951.[14] The engine features rocker arms that were mounted transversely on its intake valves but in a fore/aft position for the exhaust valves, which made it more compact and allowed easier installation into the car.[12] It is mated to a custom Dynaflow automatic transmission.[6]

During testing, Chayne claimed that the XP-300 achieved a top speed of 140 miles per hour (230 km/h) in the hands of Buick general manager Ivan Wiles.[1][3][4] Chayne also used the car personally, and reached at least 110 mph (180 km/h) in it himself.[1]

The XP-300 was displayed at auto shows across the United States, where it became a popular fixture with attendees as well as the press.[1] It was displayed at the Chicago Auto Show in February 1951, despite not yet being completely finished.[4] Later that year, it was displayed at the GM Proving Grounds alongside the Le Sabre.[4] The two cars were then displayed together during GM's 1953 Motorama tour.[4] During its unveiling in Santa Ana, California, Chayne called the car "undoubtedly the safest, most comfortable, high-performance car on the road today".[6] The XP-300 accumulated nearly 10,400 miles (16,700 km) of driving, although it did not drive as far as the more publicized Le Sabre.[4] The XP-300 was also insured for $1 million.[7]

Together with the Le Sabre, the XP-300 pioneered the wraparound windshield.[1][12] While the XP-300 inspired the design of the front and upper quarter panels of 1953 and 1954 Buicks,[15] and the headlight styling, wraparound windshield, and adjustable front seats of the 1954 Buick line,[16] it ultimately had much less influence on future car design than the Le Sabre.[15] The Le Sabre, on the other hand, inspired the tailfins on 1953 and 1954 Pontiacs as well as 1957 Cadillacs, the gull-wing bumpers on various Cadillacs, and even European designs such as the Spohn-bodied Veritas and the ZIS-112.[15]

In 1966, the XP-300 was refurbished and donated to the Alfred P. Sloan Museum in Flint, Michigan.[15] In 1985, it was at the Sloan Museum alongside the 1956 Buick Centurion, Buick Wildcat II, Buick Y-Job, Cadillac Cyclone, and General Motors Le Sabre.[17] In 1991, it was exhibited at the Museum of Transportation in Brookline, Massachusetts, along with four other GM cars.[10] As of 2018, it was on display at the Sloan Museum, along with four other Buick concept cars.[1][3]