A single road test can make or break a car’s reputation. Sometimes the disappointment is deserved, like in the infamous case of the Vector W8. This car constantly malfunctioned, disappointing its creator Jerry Wiegert and enthusiasts alike. However, some tests unfairly tarnish a vehicle’s image by overlooking critical details. Take a look at a 1971 comparison by Motor Trend, which featured three Mustangs: a Boss 351, a 429 Cobra Jet Mach 1, and a standard hardtop.
Focusing on the Boss 351 and the 429 Cobra Jet, the tests showed surprising results. Even with 370 horsepower and 450 lb-ft of torque, the 429 Cobra Jet lagged behind the Boss 351 in acceleration. The Boss zipped to 60 mph in 5.8 seconds, while the Cobra Jet took 6.5 seconds. In the quarter-mile, the Boss was faster at 13.8 seconds compared to the Cobra Jet’s 14.61 seconds.
This disparity raises questions. Was the 429 Cobra Jet’s power exaggerated? Not necessarily. The Boss had a better final drive ratio (3.91:1) and a four-speed manual transmission, while the 429 Cobra Jet used a three-speed automatic, which limited its performance. Additionally, the 429 Cobra Jet had air conditioning, a drain on power that the Boss did not experience. In short, the comparison wasn’t fair.
Another factor was the Boss 351’s aftermarket headers. These enhancements gave it an edge, making it hard to compare apples to apples. Tire performance also mattered; while both cars had F60-15 tires, the heavier 429 might struggle for traction compared to the lighter Boss. With better tires, the outcomes could have been quite different.
Other tests revealed similar results. Sports Car Graphic recorded a quarter-mile time of 14.6 seconds with a four-speed manual but on narrower tires. Meanwhile, in another test by Super Stock, the 429 Cobra Jet managed a 13.97-second quarter-mile performance.
For those seeking a bit more power, Ford offered a Super Cobra Jet 429, boasting upgraded features like a solid-lifter cam and higher airflow carburetors, upping its power to an estimated 400 hp. Unfortunately, tests for these models are scarce. A single test showed it clocking in at 13.4 seconds despite some performance handicaps, hinting at even greater potential.
Interestingly, the legacy of these tests still affects collector car values. The Boss 351 commands higher prices today, often thousands more than the 429 Cobra Jet. Discussions on forums often highlight the perceived superiority of the Boss despite the 429’s sturdy specifications. This situation highlights a recurring theme in automotive history—the disparity between real-world performance and test outcomes. The Mustang community continues to feel these echoes decades later.
As the conversation evolves, it’s important to remember the nuances that influence car performance and reputation. The differences in equipment, design, and even the methods used for testing can greatly affect outcomes. For classic car fans and potential buyers, understanding these elements can provide clearer insights into the true value of these iconic vehicles.
For more on vintage Mustangs and their performance measures, check out Hagerty.
