The 1960s are considered the golden age of the American muscle car, but the 1968 Pontiac Firebird Sprint featured on this episode of "Jay Leno's Garage" shows that Detroit automakers weren't only focused on V-8s and quarter-mile times.

Instead of the V-8 engines offered in other performance versions of the Firebird, the Sprint had an inline-6 under its hood. This was an upgraded version of the engine offered in base versions of the Firebird, sporting a single overhead cam head, four-barrel carburetor, and performance exhaust. In the Sprint, it's coupled to a 4-speed manual transmission the driver works with assistance from a hood-mounted tachometer.

As Leno tells it, then-Pontiac boss John DeLorean was a fan of the Jaguar E-Type (which launched in 1961 with a dual overhead cam inline-6) and wanted to build a competitor. While Pontiac did ultimately build a concept version called the Banshee, General Motors wouldn't approve a production model, fearing it would compete with the Corvette.

1968 Pontiac Firebird Sprint convertible on Jay Leno's Garage

1968 Pontiac Firebird Sprint convertible on Jay Leno's Garage

Instead, DeLorean launched the Firebird Sprint, intending to take on the E-Type with his own inline-6 (albeit in a larger, heavier car) and an emphasis on handling. Because the Firebird Sprint was meant to compete with European sports cars, it even got "4.1-liter" badging, instead of the cubic-inch displacement measurement that was typical for U.S. automakers at the time.

The Firebird Sprint may have satisfied DeLorean's legendary ego, but it was not a commercial success. It made less power (about 220 hp) than a V-8 Firebird of the time, but cost more, Leno pointed out. Consequently, the Sprint is now very rare. Keep in mind that there was never an equivalent version of the Firebird's Chevrolet Camaro twin, which shared the GM F-body platform.

Leno acquired his Firebird Sprint convertible in 2019, and put it back on the road after a light restoration and some modern upgrades for drivability. Watch the full video for more details of this unusual Pontiac, and to heard that straight-6 sing.