Home Cars Surprise Performance: Fast Cars With Suspect Horsepower Ratings

Surprise Performance: Fast Cars With Suspect Horsepower Ratings

Vukasin Herbez June 22, 2020

Photo Credit: Mecum

5. Hemi 426

From 1966 to 1971, the Chrysler Corporation produced the infamous Hemi 426 engine, the definitive muscle car engine of all time. It was the top-of-the-line engine option for select Dodge and Plymouth muscle cars. It was the most expensive and also the most powerful. The name, “Hemi,” comes from hemispherical combustion chambers inside the heads of the engine and “426” is its displacement measured in cubic inches. This engine was officially rated at 425 hp throughout its lifespan, but everybody knew this number was a joke. The Hemi technology allowed this engine to achieve a much higher rpm range than the standard big-block V8 engine of the day, and that meant more horsepower and torque.

Photo Credit: Hemmings

Big valves allowed much better airflow, which also helped the power. Straight from the box, the Hemi 426 could produce around 500 hp without any problem. Most owners decided to do some modifications like new carburetor jets to easily get 550 hp without much work. That’s more than 100 hp above the factory specifications. Horsepower has always been a way to distinguish fast cars from slow ones, but the statistics have not always been real. Although the car makers have their reasons, it’s easy to test them to find out the actual horsepower. Thankfully, today’s carmakers are more truthful about horsepower.

Photo Credit: Hagerty

4. Ford Mustang Boss 302

The third redesign of the Mustang appeared for the 1969 model year, and the car grew again. Ford produced it for only two years in 1969 and 1970. The Boss 302 featured a 302 V8 engine conservatively rated at 290 HP. The real output was closer to the 350 HP mark though.

Photo Credit: Mecum

The Boss 302 was a model Ford intended for racing in the Trans-Am championship. Apart from the blackout hood, spoiler on the trunk, and other details, it featured a stiff, track-tuned suspension, a close-ratio gearbox, and a high revving engine. The car was light and without any unnecessary luxuries, so the performance was impressive.

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3. Pontiac 400 Ram Air IV

Back in the late ’60s, Pontiac’s Ram Air engines were one of the hottest mills in the muscle car class. This engine featured a four-barrel carburetor with the famous Ram Air induction system. The ratings were 360 HP in its RA III form. They installed those engines in GTOs, making them the perfect street racers of the era. However, in 1969, Pontiac presented the Ram Air IV version of the same engine with the same advertised horsepower rating of 360 HP. The two engines looked the same, but the RA IV had much different internals underneath.

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It had different engine heads, camshafts, and valves. It also had more compression and a higher rev limit. The Ram Air IV was capable of much more than 400 HP. However, the factory decided to rate it at 360 HP for insurance reasons. Unfortunately, the Ram Air IV was an expensive option so Pontiac didn’t make many of them.

Photo Credit: Tuning Blog

2. Ford Mustang SVT Cobra

Inspired by the wild SVT Cobra R’s from the ’90s, they didn’t name the 2003 model “R” since it wasn’t limited in production. Ford made it available to the public rather than just racing drivers and private teams. However, this SVT Cobra was an interesting, important model for the Mustang dynasty since it featured two firsts. It was the first factory supercharged engine with an independent rear suspension. For the SVT, Ford took the standard 4.6-liter block and mounted different heads and a supercharger to get 390 HP and 390 lb-ft of torque.

Photo Credit: Car Scoops

They named the engine the “Terminator.” The rumor was that it delivered more than the advertised 390 HP. In fact, it was much closer to 430 HP. To handle all that power and torque, Ford equipped the SVT Cobra with an independent rear suspension setup like the first Ford GT. This helped stability at high speeds and hard launches, making this Mustang handle like a dream.

Photo Credit: Hagerty

1. Buick GNX

The ’80s were the dark ages of muscle cars and American performance, but there were a few bright moments. One of the cars that restored faith in muscle car movement in the ’80s was the mighty Buick GNX. The story of this model is an interesting one. Back in 1982, Buick started experimenting with turbocharging its line of standard V6 engines. The results were satisfying, so engineers got permission to develop a performance version with better acceleration figures. Soon there was a Buick Grand National with 175 HP, which wasn’t impressive but was a start.

Photo Credit: Motor 1

In the next couple of years, the Grand National got a bigger engine and more power, jumping from 175 HP to 200 HP and finally to 235 HP. With those numbers came the acceleration times of under six seconds. Those black Grand Nationals were quick cars. But in 1987 came the ultimate version Buick called the Grand National Experimental, or GNX for short. It featured the same 3.8-liter turbocharged V6 but with 275 HP and 0 to 60 mph times of 4.7 seconds. Lots of car enthusiasts claimed the GNX produced at least 300 HP since it was extremely fast. At that moment, Buick GNX was the fastest accelerating production model in the world. At $29,000 it wasn’t a bargain, but there is a widespread legend about owners who paid the lease on these cars by street racing them for money.

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