Few eras in automotive history burned as bright as the golden age of the American muscle car. Today, those machines remain as captivating as ever — rolling proof that horsepower, attitude, and sheer audacity can transcend decades. At the heart of that story sits a handful of ultra-rare survivors that remind us just how wild Detroit's ambitions really were. One of the wildest of all came from Plymouth, a brand better known at the time for sensible family transportation than tire-shredding performance.Models like the Pontiac GTO, Ford Mustang, and Chevrolet Chevelle SS 396 were capturing the imagination of a generation, establishing the template for American performance cars.These bold, aggressive machines found eager buyers among young professionals enjoying newfound prosperity and working-class enthusiasts seeking American performance they could actually afford. Against this backdrop of high-octane excitement, Plymouth recognized an opportunity. The company's Belvedere had built a reputation as a sensible choice — popular with family buyers seeking practicality and fleet managers outfitting police departments. Yet Plymouth saw potential to transform this unassuming platform into something extraordinary: an upscale performance variant that would become the most formidable and elusive Plymouth of the entire decade. The 1967 Plymouth GTX Hemi Convertible Is The Rarest Plymouth Muscle Car Produced In The '60s Mecum The Belvedere GTX was no small-block V8 boulevard rumbler — the car was offered exclusively with a choice of two big-block engines: the 440ci and the 426 Hemi.Inside, the GTX leaned more toward luxury car than outright street racer, featuring upmarket trim and a generous standard equipment list that included a tachometer on the center console, bucket front seats, and embossed vinyl upholstery. The Plymouth GTX was very much an upmarket muscle car convertible with a Hemi heart.Mecum Externally, Plymouth gave the GTX a unique grille, as well as scoops and optional stripes. It was introduced in 1967 as a fairly niche model at the top of the Plymouth range. This muscle car legend was called a 'gentleman's hot rod' by Plymouth, but the newly-titled GTX wasn't quite as elegant as the nickname suggested — it was a fire-breathing monster. The Hemi Was A Fearsome Race Engine Dropped Into A Luxury Car Mecum The Hemi, known as the Elephant in some circles, was already gaining mythical status, with a domination in NASCAR that ultimately led to a ban. It was seemingly too ferocious for the streets, with its 425 hp at 5,000 rpm and 490 lb-ft of torque at 4,000 rpm. Those figures were almost certainly conservative — quoted low for insurance purposes — with 500 hp being a more realistic estimate. The decision to drop this monster powerplant into the mundane Plymouth Belvedere certainly raised a few eyebrows. Only 17 1967 GTX Convertibles Were Ever Sold Mecum If the power outputs were controversial, the pricing was off-putting. The 426 Hemi was a costly option; ticking that box added an extra $564 to the sticker. To put that into perspective, the standard two-door hardtop was priced at $3,178, making the engine a near-20% premium. The convertible body added a further $240, meaning buyers had already bumped the price up by roughly 13% over the regular solid-roof car before specifying the Hemi.For anyone taking performance driving seriously — whether at the drag strip or on track — a 500-hp convertible would never be the first choice, owing to the inherent compromise in structural rigidity that comes with a drop-top body. Of the 680 Plymouth GTX convertibles sold in 1967, just 17 were equipped with the Hemi V8, though some estimates put the figure as low as 14, making this one of the rarest muscle cars of its era. A Closer Look At the 426 Hemi Engine Mecum Auctions It's hard to think about muscle cars without thinking about the 426 Hemi. The Mopar-engineered big-block Hemi V8 is a legendary powerplant that has proven remarkably enduring, having been fitted in more recent years to everything from the Jeep Wrangler Unlimited Rubicon 392 to the Chrysler 300 SRT-8, as well as producing 1,000 hp in 6.2-liter Mopar 426 HEMI 'Hellephant' crate-engine form.In the 1960s, the Hemi V8 was feared on both streets and racetracks, its deep, menacing purr being the last thing many drivers wanted to hear at a red light. The 426 Hemi engine — often called the "Elephant Engine" on account of its sheer size and power — traces its lineage to 1951, when Chrysler introduced its first Hemi, known as the "FirePower" V8. The name derived from its overhead-valve hemispherical combustion chambers, a design that dramatically improved airflow and thermal efficiency. The Hemi Had Achieved Legendary Status In Race Cars Chrysler 426 HEMI Plymouth GTX Hemi Convertible Specs The 426 Hemi was introduced in 1964 specifically for racing applications, achieving almost immediate success by winning the Daytona 500 that year. Its dominance proved to be its own undoing on the track, however, after Richard "The King" Petty proved invincible in a Hemi-powered Superbird and NASCAR imposed stricter rules, banning competitors from using an engine that lacked a production street version.But NASCAR's loss was muscle car fans' gain. In 1966, Chrysler made the 426 Hemi available in street-legal vehicles, debuting in the Plymouth Belvedere and Dodge Coronet. One Coronet Hemi was recently uncovered in storage after 37 years. The street-version Hemi featured a lower compression ratio of 10.25:1 and a milder timing chain, but even in detuned form it remained one of the most potent powerplants ever fitted to a production muscle car — a true legend of the genre.Transmission options were either a four-speed manual or the TorqueFlite automatic — ten of the convertibles were ordered with the automatic gearbox. Here's How Much A 1967 Plymouth GTX Hemi Convertible Will Cost You Mecum Pricing Details When New Standard GTX Two-Door Hardtop: $3,178 Convertible Body Option: $240 Hemi Engine Option: $564 Naturally, the 17 examples of 1967 Plymouth GTX Hemi Convertibles don't come up for sale very often. That said, even when one of these rare-as-rocking-horse-manure 426-powered ragtops does reach the market, prices aren't quite as eye-watering as some might expect — though deep pockets are still very much required. A Good Condition Example Will Fetch $123,000 Mecum A Plymouth GTX Hemi Convertible in good condition will cost on average around $123,000, according to Hagerty Valuation Tools. The earliest known Hemi GTX Convertible — an example built on September 21, 1966, and delivered on October 11, 1966 — came up for sale at Mecum Auctions and is believed to be the very first GTX fitted with a Hemi.The story goes that the car had been ordered new through Manhattan Chrysler Plymouth, Inc., by Chrysler employee Rene Sergei Tennenbaum as a tow vehicle for his "Mad Russian" Max Wedge Super Stocker. The car was completely restored, and the 426 Hemi engine was rebuilt to correct late-1966 specifications, including dual 4-barrel carburetors and factory engine components.Sources: Hagerty, Hemmings, Barrett-Jackson, Mecum.
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