1972 Plymouth Road Runner GTX

The Plymouth Road Runner is a mid-size car with a focus on performance built by Plymouth in the United States between 1968 and 1980. By 1968, some of the original muscle cars were moving away from their roots as relatively cheap, fast cars as they gained features and increased in price. Plymouth developed the Road Runner to market a lower priced, basic trim model to its upscale GTX.

Origin

Plymouth paid $50,000 to Warner Bros-Seven Arts to use the Road Runner name and likeness from their Wile E. Coyote and The Road Runner cartoons (as well as a “beep, beep” horn, which Plymouth paid $10,000 to develop). The Road Runner was based on the Chrysler B platform (the same as the Belvedere and Satellite), as a back-to-basics mid-size performance car.

Second Generation Roadrunner (1971–1974)

1972 saw new emission regulations drive power down and 1/4 mile times up. The 1972 model was nearly identical to the 1971 with a few minor changes. The grille design was cleaned up, and the tail lights were changed to match the new aerodynamic look of the grille. Side marker lights changed from the flush mounted side markers to the surface-mounted units that were adopted across the entire Chrysler line-up for the 1972 model year. The optional bumper guards for 1972 included a rubber strip surrounding the tail lights and a rubber strip below the grille. The big differences came in the cutting back of performance options for the car. The suspension, rear axle ratios (a 3:55 ratio was the tallest available), and most noticeably the engines changed, with the big-block 383 being replaced by a larger-bore (and lower performance) 400 CID version as the standard engine. The small-block 340 CID as well as the performance version of the 440 CID engine (with a 4-barrel carburetor, performance camshaft, and dual exhausts) were also available, and for the last time a 4-speed manual transmission could be paired with any of the three engines. All of the engines suffered a drop in compression ratios to allow use of low-lead/no-lead gas and to meet the first round of emissions regulations. The 280 hp (209 kW) 440 engine was the basis for the Road Runner GTX (the GTX was no longer a separate model) and was available on Road Runners from 1972 to 1974. 

The 1971-72 Road Runner sheetmetal was used by several NASCAR racing teams for their racecars and ran well on the circuit during the 1971-74 seasons. Richard Petty won the championship both in 1971 and 1972 using the Road Runner-based cars, winning 30 races over the two seasons.

For 1972 power ratings on all engines looked much lower on paper due to the new SAE net measurement system. The famed 426 Hemi was discontinued for 1972, and only five 440 Six Barrel equipped cars were produced before this engine option was dropped (it was determined the 440 six-pack could not meet the stricter 1972 emissions regulations) in the fall of 1971.