“Moonshiners put more time, energy, thought, and love into their cars than any racer ever will. Lose on the track, and you go home. Lose with a load of whiskey, and you go to jail.” – Junior Johnson

Perhaps that mindset is why Junior Johnson’s famous Mystery Motor Impalas claimed seven wins, 13 top fives, 14 top tens, and nine pole positions on their way to leading nearly every one of the 33 races they started in the 1963 Grand National season. Or perhaps it’s because 1960s Chevrolet, such a dominant force that some in the government wanted to split it from parent General Motors, had developed an engine, and car, that changed the course of American motorsports and culture.

The year 1963 was a notable one for General Motors and the American automotive industry. “Win on Sunday, Sell on Monday” was influencing everything from the showroom to the executive suite, and the Big Three were in an all-out power war, both at the track and on the street. Chevy’s stalwart W-block had reached its full potential, and the brand knew it needed to bring some serious firepower to compete with Chrysler’s upcoming Hemi and Ford’s upcoming “Cammer” So, in addition to Zora Arkus-Duntov’s fabled Corvette Grand Sports, the boys in engineering cooked up a little something special for circle tracks and drag strips. Enter the Mark II 427 or, as it would be affectionately nicknamed, the Mystery Motor.

Full Factory Support

At the beginning of 1963, Chevrolet was working directly with two of NASCAR’s biggest and most brazen stars: Smokey Yunick and Junior Johnson. In exchange for helping the brand develop a new big-block, both teams would receive showroom stock Impalas and several 427 cubic inch engines that made well over 500 horsepower straight off the assembly line. The result was a full-size bruiser of a race car that, thanks to its massive power advantage, could win pretty much anywhere it rolled off the trailer.

A part of the extraordinary RK Collection, this particular Mystery Motor Impala is one of three cars Junior Johnson fielded for the 1963 NASCAR Grand National season. Preserved for over 60 years in as-raced condition, the Chevy was originally used as the team’s primary superspeedway car. In addition to setting a 165.183 MPH qualifying record at Daytona, the Impala logged its final victory at Charlotte Motor Speedway in the 1963 National 400 in front of 46,531 fans.

But wait …didn’t General Motors ban factory racing in 1963, you ask? Yes, indeed they did. In fact, they backed out of Junior Johnson’s deal before the season even began. But ole Junior had a few tricks up his sleeve. First, he teamed up with one of the best NASCAR engine builders of all time, Raymond Fox, to keep his big-blocks in top shape. Then, knowing that NASCAR required Chevrolet to supply new engines to competitors for analysis, he traveled to Charlotte’s Holman Moody to buy their Mystery Motor. Then he visited former competitor Carl Kiekhaefer, eventual founder of Mercury Marine, to buy a few Mark II blocks he had requested for race boats. Ultimately, according to Johnson, his team ended up with three Impalas and seven Mystery Motor 427s.

It Really Is A Stock Car

Of course, the showroom stock Impalas Chevrolet sent the teams would undergo pretty serious mechanical transformation once they arrived at the race shops. Make no mistake, at that point NASCAR was still very much stock car racing, but the teams strengthened various components of the cars so they could handle hours and miles of being driven at the absolute limit.

The car features a truck arm rear suspension that was cutting-edge technology for 1963. This suspension is very close to the setup that virtually all NASCAR competitors would eventually adopt and run for decades.

Take a look under this Chevy and you’ll see a truck arm rear suspension that, in 1963, was considered cutting edge. So cutting edge, in fact, that it is very close to the setup virtually all of NASCAR’s competitors would eventually adopt and run for decades. Junior Johnson was running big coil springs, likely a 1,200-1,400lb. in the right rear of this car, when large operations like Petty Enterprises were still running leaf springs and torsion bars. The rest of the Impala’s rear-clip includes big hubs, a panhard bar, and a requisite 9-inch housing that was sourced from a ¾-ton Ford truck.

Perhaps the most impressive aspect of this awesome fab work is that it was meticulously installed by Junior Johnson and his associates on the floor of the shop with a welder and jack stands. As you might already know, Junior Johnson & Associates, as an official entity, would evolve to employ NASCAR crew legends Mike Beam, Tim Brewer, Jeff Hammond, Travis Carter, and Tim Roberts, among others.

Back in the 1960s, stock car racing meant racing stock cars, and NASCAR allowed very few modifications to factory bodies. That’s exactly what you’ll see when you look at the outside of this as-raced Impala. Aside from decals, not much has changed from when it rolled off Chevrolet’s assembly line as a full-bodied steel coupe. The car’s headlights and taillights have been removed, per NASCAR rules. Hood and trunk pins have been installed in the name of ease and safety. There are no mirrors, and, according to Johnson, NASCAR would allow them to remove the windshield wiper arms but not the wiper motors. Otherwise, this is a stock 1963 Chevrolet Impala SS all the way down to its ornate quarter emblems and familiar header and decklid crests.

The interior of this Chevy highlights just how much of a different era this was in terms of the men who drove these cars and the cars those men drove. The lightened cockpit has been reduced to a factory dash and a factory driver’s seat, which includes a shoulder harness that, according to Johnson, NASCAR initially made him remove. The steering wheel is a big factory unit that Johnson and his associates wrapped in fan belts and electrical tape. A beefy roll bar adds minimal protection to the driver, at least, compared to today’s standards. The doors are covered in fitted metal panels that the crew, ingeniously, sourced from a pile of scrap coolers at sponsor Holly Farms’ poultry facility. The car retains all of its window cranks because, as Johnson stated, he preferred to race with the windows rolled up at superspeedways for maximum aero advantage – a statement that isn’t the least bit surprising since Johnson is widely credited as the first stock car driver to understand and utilize drafting techniques.

The Last American Hero

Robert Glen Johnson Jr. was one of seven children born to Wilkes County moonshiner Robert Glen Johnson Sr. The Johnson family, settling in the hills of North Carolina in the 1600s, had a long history of making hooch, and Robert Sr. would eventually get caught with 400 gallons of illegal liquor. That bust, one of the largest in state history, meant Senior would end up spending 20 of his 63 years in prison. It should come as no surprise, then, that Junior became a very successful shine runner and, while the revenuers would eventually catch up to him, it would be because of a still in his house, not because they were ever fast enough to rundown his infamous ‘40 Ford.

After his run-in with the law, Johnson decided to put his driving skills to use on NASCAR’s rowdy short tracks. In May of 1955, he held off Tim Flock to win a 200-lap, $1,000 feature at Hickory Motor Speedway, a local dirt track. That would be the first of five wins in his 36 starts in the 1955 Grand National season, which resulted in a sixth place podium in points. Over the following decade, Johnson would claim 45 more victories before retiring to become one of the series’ most successful team owners. As the leader of Junior Johnson & Associates, he would win six championships: three with legend Cale Yarborough, and three with legend Darrell Waltrip. He would also celebrate 132 victories through a roster of epic driving talent that included LeeRoy Yarborough, Bobby Allison, Bill Elliot, Neil Bonnett, Terry Labonte, Geoff Bodine, Jimmy Spencer, and Sterling Marlin.

In short, Johnson wasn’t just hailed as The Last American Hero by author Tom Wolfe – a write-up that would eventually inspire a major motion picture. Through a lifetime of guts, instinct and ingenuity, he clawed his way into the Motorsports Hall of Fame, the list of 50 Greatest NASCAR Drivers of All Time, and the first class inducted into NASCAR’s Hall of Fame.

Mystery Motor Magic

At Chevy, there were two primary reasons for developing a fresh big-block. In a world with Chrysler Hemis and Ford Cammers, the brand needed something that went beyond the performance envelope of the tried-and-true W-block. And with Zora Arkus-Duntov forging the Corvette into a world-beating sports car, the brand needed something compact enough to fit in the freshly introduced Sting Ray. Because of the Corvette’s relatively low hood, Chevrolet did not pursue hemispherical combustion chambers, instead utilizing 90-degree cylinder decks and canted valves that would inspire the term “porcupine heads”.

The Z33 Mark II or, internally, Mark IIS to denote its status as a stroked 409, was one of four big-block prototypes tested. In addition to a single Holley 4-barrel carburetor, it incorporated strengthened connecting rods, high-compression pop-up pistons, screw-in rocker studs, and an aluminum, high-rise intake. The basic philosophy was to optimize the engine’s high RPM air flow.

The Mystery Motor program wasn’t solely destined for NASCAR competition. According to folklore, Chevrolet produced components for up to 60 big-blocks and, while no official production number exists, experts believe anywhere from 15 to 40 Mark IIs were actually assembled. Perhaps as famous as the Junior Johnson Impalas were the Mark II-powered Corvette Sting Rays fielded by Mickey Thompson in the 1963 Daytona 250 American Challenge Cup Race. That said, the Mystery Motor was, at its core, an experimental program that had yet to be vetted in the rigors of competition and ceded factory support very early. That’s why Johnson is on record saying, “If it lasted, it won the race,” and that’s probably also why he knew it would be crucial to partner with an engine builder like Ray Fox.

In addition to blueprinting this Impala’s 427, Ray had the ability to tune the Mystery Motor far beyond its 500 horsepower factory rating. Because the Mark II would never make its way into a production car, NASCAR eventually banned it from competition. In the end, most of the engineering tricks Chevy learned from unofficially supporting the Mark II racing programs showed up in the Mark IV engines we all know and love.

Preserve And Persevere

As for the fate of this particular Mystery Motor Impala, well, Junior did what many farmers do with old equipment. He took it home and parked it in a barn. That’s exactly where the car would sit until a sale was negotiated with RK Collection in early 2012.

More than just a race car, Junior Johnson’s 1963 Mystery Motor Impala is a literal representation of why so many of us spend our lives enamoured with all things automotive. It transfixes us in a time when Detroit was defined by brilliance, our beloved hobby was led by larger-than-life personalities, and racing was fueled by sheer grit and determination. More than just a piece of motorsports history, this car embodies the spirit of American ingenuity and success. From cutting-edge champion to as-raced relic, it reminds us that true icons aren’t flawless – they’re forged through inspiration, struggle, and the relentless pursuit of success.