Plymouth Superbird

The short-lived Plymouth Road Runner Superbird was a highly modified version of the Plymouth Road Runner with well known graphics and horn. It was the factory's follow up stock car racing design for the 1970 season to the Dodge Charger Daytona of 1969, and incorporated many engineering changes and modifications (both minor and major) garnered from the Daytona's season in competition on the track. The car's primary rival was the Ford Torino Talladega, which in itself was a direct response to the Mopar aero car. It has also been speculated^[who?] one major motivating factors in the production of the car was to lure Richard Petty back to Plymouth. Both of the Mopar aero cars famously featured a protruding, aerodynamic nosecone, a high-mounted rear wing and, in the case of the Superbird, the same horn which mimicked the Road Runner cartoon character.
Developed specifically for NASCAR racing, the Superbird, a modified Road Runner, was Plymouth's follow-on design to the Charger Daytona fielded by sister company Dodge in the previous season. The Charger 500 version that began the 1969 season was the first American car to be designed aerodynamically using a wind tunnel and computer analysis, and later was modified into the Daytona version with nose and tail. The Superbird's smoothed-out body and nosecone were further refined from that of the Daytona, and the street version's retractable headlights added nineteen inches to the Road Runner's original length. The rear wing, was mounted on tall vertical struts that put it into less disturbed air thus increasing the efficiency of the downdraft that it placed upon the car's rear axle. For nearly thirty years the mathematic formula used to determine the exact height of the enormous wing was thought to be a highly guarded Chrysler secret. However, in the 1990's a retired Chrysler project engineer admitted publicly that the height was determined in much simpler fashion: It was designed to provide clearance for the trunklid to open freely. The rear-facing fender scoops were incorporated in an effort to ventilate trapped air from the wheel wells in order to facilitate brake cooling.

NASCAR's homologation requirement demanded that vehicles to be raced must be available to the general public and sold through dealerships in specific minimum numbers. For 1970, NASCAR raised the production requirement from 500 examples to one for every two manufacturer's dealers in the United States; in the case of Plymouth, that meant having to build 1,920 Superbirds. Due to increasing emissions regulations, combined with insurance hikes for high performance cars, 1970 was its only production year.
"Superbird" decals were placed on the outside edges of the spoiler vertical struts featuring a picture of the Road Runner cartoon character holding a racing helmet. A smaller version of the decal appears on the driver side headlight door. Superbirds had three engine options: the 426 Hemi V8 engine, the 440 Super Commando with a single 4-barrel carburetor, or the 440 Super Commando Six Barrel with three two-barrel carburetors. Only 135 models were fitted with the 426 Hemi. As the 440 was less expensive to produce, the "Street" version of the 426 Hemi engine used in competition was homologated by producing the minimum number required.
On the street, the nose cone and wing were very distinctive, but the aerodynamic improvements hardly made a difference there or on the drag strip. In fact, the 1970 Road Runner was actually quicker in the quarter mile and standard acceleration tests due to the increased weight of the Superbird's nose and wing. Only at speeds in excess of 90 mph (140 km/h) did the modifications show any benefit.

The Superbird's styling proved to be a little extreme for 1970 tastes (many customers preferred the regular Road Runner), and as a consequence, many of the 1,920 examples built^[3] sat unsold on the back lots of dealerships as late as 1972. Some were converted into 1970 Road Runners to move them off the sales lot. In recent years, however, the Superbird has become quite valuable. A Superbird can fetch anywhere from US$300,000 to US$2,000,000^{[citation needed]}. On BarrettJackson, bids for original Superbirds crossed US$1,200,000.^{[citation needed]} Some manufacturers produce Superbird conversion kits for 1970 Road Runners and Satellites.^{[citation needed]} Kits are also available for non produced 1971 and 1972 bodies for the Superbird.^{[citation needed]}
The Superbird and the Dodge Charger Daytona were each built for one model year only (1970 and 1969 respectively).