When talking about muscle cars, enthusiasts usually refer to the beefed-up compact and mid-size coupes of the late 1960s. That's when the muscle car era reached its peak, with tens of vehicles available from all Detroit-based automakers. But the muscle car's roots can be traced all the way back to 1949 when Oldsmobile dropped the Rocket V8 engine in the 88.
The concept can also be expanded to full-size cars, many of which gained powerful drivetrains long before muscle cars like the Ford Mustang, Chevrolet Camaro, and Plymouth Barracuda became the norm. The Chevrolet Impala was one of them.
A rather mild land yacht at its introduction in 1958, the Impala quickly joined the trend of the era and became increasingly more powerful with each generation. Rated at 280 horsepower in 1958, the 348-cubic-inch (5.7-liter) V8 came with 350 horses on tap in 1960. But the Impala truly stepped into the high-performance realm in 1961, when Chevrolet introduced the Super Sport (SS) option.
Originally available on any Impala, the SS package was mostly an appearance bundle at first, but it also came with a brand-new, 409-cubic-inch (6.7-liter) V8 rated at 360 horsepower. But Chevrolet took things up a notch in 1963, just before GM announced a withdrawal from competition for all its brands.
Photo: Mecum Auctions
As the drag racing scene was leaving a big mark on high-performance production models, Chevrolet put together a race-oriented Impala to compete against the Ford Thunderbolt. That's how the Regular Production Option (RPO) Z11 was born.
Created for drag racers and NASCAR enthusiasts, the Z11 was essentially a lighter Impala with a bigger, more powerful V8. The latter was a 427-cubic-inch (7.0-liter) derived from the existing 409 mill and equipped with a longer stroke, a two-piece, high-rise aluminum intake, dual four-barrel carbs, and a special cowl induction system. Thanks to a 13.5:1 compression ratio, the 427 produced a whopping 430 horsepower and a staggering 575 pound-feet (780 Nm) of torque.
That's slightly more than the legendary 426 Hemi V8 engine that Mopar introduced a few years later!
But the Impala Z11 wasn't just about power and torque. To become a competitive drag racer, it also had many of its steel parts built from aluminum. The fenders, bumpers, engine hood, brackets, grille, and braces were all made from weight-saving material.
In addition, Chevrolet stripped the car off its radio, heater, sound deadening material, and front sway bar. The result was a 300-pound (136-kg) reduction over the regular Impala.
Tipping the scales at 3,500 pounds (1,588 kg), an impressive figure for a 17.5-foot-long (5.3-meter-long) full-size, the Z11 needed only 4.3 seconds to hit 60 mph (97 kph) and covered the quarter-mile in just 10.8 clicks. That was faster than most U.S.-built production cars at the time. It was also the first stock car to exceed 120 mph (193 kph) in a quarter-mile run.
Photo: Mecum Auctions
But like many RPO-equipped, high-performance Chevys of the era, the Impala Z11 was far from cheap. The package added $1,240 to the price of a regular Impala, taking the sticker to $4,000 before any other options were selected. As a result, only a few cars were built. Most sources claim that Chevrolet assembled only 57 Z11s, which makes it the rarest Impala ever offered.
While some of them didn't make it to this day, most cars are still around to tell their stories almost 60 years later. Impressively enough, the first Impala Z11 ever built is among those that survived. And it's as original as they get.
I'm talking about "Old Reliable," the Z11 that was used as a mule before production kicked off. Once other Impalas started rolling off the assembly line, "Old Reliable" was taken to the track and won 90% of its races in 1963 in 1964. Such performance was unheard of in those days and helped cement the Z11's reputation as a fast and reliable factory performance car.
With fewer than 50 of them still around, the Impala Z11 is now a prized-collectible and arguably the most expensive of its kind. They rarely show up on the auction block, but when they do, they command prices over $350,000.
In 2017, a black-painted Z11 (one of only two built this way) changed hands for a whopping $432,000. Also in 2017, "Old Reliable" sold for $525,000.
While the Impala nameplate lived on for many decades after the Z11 was discontinued, Chevrolet never built another one like it. GM did offer the Impala Z24 with up to 425 horsepower in the late 1960s, but it was devoid of the lightweight and race-bred components that helped the Z11 achieve glory at the drag strip. And it all happened six years before Chevy developed the 1969 COPO Camaro.
Ask Ciprian about cars and he'll reveal an obsession with classics and an annoyance with modern design cues. Read his articles and you'll understand why his ideal SUV is the 1969 Chevrolet K5 Blazer. Full profile
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