There has been a longstanding suspicion within the automotive community concerning factory-published power output numbers of the muscle cars of the 1960s and 1970s. For decades the evidence that fueled this suspicion was confined to automotive enthusiasts truly in-the-know, enthusiasts who build motors themselves and know the ins and outs of automotive performance. No longer; automotive historian Roger Huntington has been compiling data on factory power output levels for years, in an effort to expose a decades-old scheme to keep horsepower ratings at a level that could be deemed “reasonable” for the average consumer.
Why would automakers want to undersell the performance of their sports cars? Doesn’t a car’s desirability increase relative to the power output ratings? There are two prominent theories that speak to these uncertainties. For one, keeping power output figures low may be an attempt to keep insurance rates lower for sports car owners, in turn making sports cars more attainable by the masses. Another theory suggests that muffled performance figures allow higher-performance vehicles to compete in less competitive NHRA classes; this would make the vehicles appear more capable than their counterparts of different marques, building the high-performance image of the brand.
The case for appeasing automotive insurance companies is easy to understand. Insurance rates are based on risk. The more powerful a vehicle’s engine, the higher the risk for accident and injury. By deflating the power output ratings of these cars, automakers were reducing the cost of ownership and expanding their potential customer base.
The National Hot Rod Association was a key player in the automotive industry of the 1960s and 1970s. Hot rods were “in”, and were prominent throughout popular culture, constantly appearing on-screen and being talked about over the radio. This massive visibility and flattery of muscle cars made them all the more desirable in the public eye. Dishonest power output ratings allowed automotive manufacturers to sell that same muscle car image that customers had idolized on-screen, but with modest-enough performance that would justify buying the car to use as a daily commuter.
Theories regarding deflated power output ratings of muscle cars of the 1960s and 1970s were a constant in automotive literature of the time, but were very rarely backed by irrefutable evidence. Now, 50 years later, Huntington’s research has brought to light what fueled the suspicions of automotive enthusiasts of the period – many muscle cars simply were more powerful than manufacturers cared to disclose.
While it may sound quite a bit like dishonesty, it would be a stretch to call it that entirely. The method by which power output figures were obtained has changed since these muscle cars were new. Currently, power output is measured by finding the highest point along the vehicle’s power curve. Back in the days of the muscle car, power output was measured at a predetermined RPM, rather than finding the peak.
Chevrolet Chevelle SS 396
The L-78 Big Block engine installed by Chevy in the SS 396 was reported to provide 375 hp at 5600 rpm. Huntington’s analysis puts it at 400 hp at 5600 rpm.
Ford Mustang 428 Cobra-Jet
The biggest discrepancy in Huntington’s research comes from Ford’s Cobra-Jet, which was sold listed at 335 hp at 5200 rpm. Huntington found the peak output to be 410 hp at 5600 rpm.
Dodge & Plymouth 440 Magnum
The 440 Magnum was originally measured at only 4600 rpm, at 375 hp. At a higher 5400 rpm, however, the Magnum reaches 410 hp.
Pontiac Ram Air 400
Advertised with 366 hp at 5100 rpm, the Pontiac Ram Air is actually capable of providing 410 hp at 5600 rpm.
Buick GSX 455 Stage 1
Sales brochures listed the GSX 445 with 360 hp at 5000 rpm, but in reality this classic car could hit 420 hp at 5400 rpm.
Ford Mustang Boss 429
The Mustang Boss 429 touted 375 hp at 5200 rpm but is in fact capable of producing 520 hp at 5600 rpm.
Dodge 440 Six-Pack
With a powerful engine that features the performance of a Hemi at half the cost, buyers were told the Six-Pack provided 390 hp at 4700 rpm. In reality, it measures 430 hp at 5600 rpm.
Oldsmobile 455 W-30
Buicks, Pontiacs and Oldsmobiles were all sold to the public as nearly interchangeable, but in fact they had completely different engines. The 455 W-30 is the cream of the crop. It advertised 370 hp at 5300 rpm, while in actuality could give 440 hp at 5600 rpm.
Dodge & Plymouth 426 Hemi
This engine was designed for NASCAR racing but offered to the public with 425 hp at 5000 rpm. Due to the excellent airflow, this motor could reach an outstanding 470 hp at 6000 rpm.
Chevrolet Corvette 427 L-88
This speed demon came with a sticker advising only racing fuel should be used in it. It was sold at 430 hp at 5200 rpm but Huntington has shown that it can reach 500 hp under ideal circumstances.