'6811/42-'70 428 CJIn the first-ever test of a factory 428 Cobra Jet Mustang, Hot Rod magazine called it "the fastest running pure stock in the history of man." Granted, the test fastback, which ran a 13.56 at 106.6 mph, was a prototype of the 50 cars that would be provided to Super Stock racers, but the hype from a respected magazine like Hot Rod was the perfect introduction to the engine designed to save Ford's performance reputation.
For nearly three years, magazine staffers pounded on Cobra Jet Mustangs. The GT500KR received most of the '68 glory, as the magazines clamored after the Shelby instead of the GT Mustang version. Hot Rod managed a 14.01 from a four-speed, 3.50-geared KR fastback, while in the same test, a heavier convertible with automatic and 3.25s ran a 14.58.
When the Cobra Jet-powered '69-'70 Mach 1s with the new Shaker hoodscoop arrived in 1969, right in the middle of the frenzied musclecar action, the automotive press praised the car with comments like, "A blend of dragster and Trans Am sedan," "Best Mustang yet," and "The new success car." With the Mach 1, the 428 Cobra Jet big-block finally had a total performance package.
The numbers backed up the image. The '69-'70 CJ Mach 1 tests all fell within the high-13-, low-14-second range. Surprisingly, the 13-second timeslips came from automatics, while the four-speed cars were in the low-14s.