Beneath the plain sheetmetal of this mid-size Plymouth sat one of the rarest engines Chrysler ever sold to the public: the 425-horsepower Street Hemi, built for NHRA stock classes and barely civilized for the street. Only 677 Belvederes were built with it in 1966, a year before the GTX name even existed to advertise what was under the hood. Buyers got forged internals, dual four-barrel carburetion, and a torque curve that demanded a reinforced rear axle. It’s the missing chapter most muscle car fans skip straight past.
The sixth generation Plymouth Belvedere is on Chrysler’s “B” mid-sized body platform.  This model could be powered with a light duty 273 cu in ((4.5 L) engine although there are four larger engine power options  on the table including the 426 cu in (7.0 L) Hemi V8  and these would be bolted to three speed automatic or a three speed standard transmission on a factory correct Belvedere.  The most powerful version of the Belvedere is an icon of the muscle car era and badged as the GTX .
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Only 677 examples of this mid-size Plymouth left the factory with the engine collectors chase hardest today — a lightweight, race-bred V8 that Chrysler barely tamed for public roads. It arrived a full year after the option first appeared on Chrysler’s B-body lineup, wedged into plain sheetmetal that gave away nothing about what sat under the hood. Buyers got a three-speed manual or TorqueFlite automatic and a rear axle that had to be reinforced just to survive the torque. Chrysler wasn’t chasing showroom glamour with this combination — it was chasing NHRA stock class records. The badge that would eventually make this exact combination famous hadn’t even been dreamed up yet. What was Plymouth’s mid-size lineup really building toward in 1966?
677 Cars, One Engine Nobody Expected to Tame
The 1966 Street Hemi made 425 horsepower at 4,000 rpm and 490 lb-ft of torque at 2,400 rpm, running dual four-barrel carburetors and forged internals lifted almost straight from Chrysler’s NASCAR and NHRA race engines. Only 677 Belvederes were built with it that year, part of just 2,730 total Street Hemi cars Chrysler built across the Belvedere, Satellite, Coronet, and Charger lineup for 1966.
The Year Before the GTX Name Existed
The GTX badge that would later define Plymouth’s mid-size muscle car wouldn’t debut until the 1967 model year. That means a 1966 Street Hemi Belvedere like this one is effectively a sleeper — the same engine combination that would earn 720 GTX orders a year later, wearing plain trim that gave no hint of what was underneath.
An Honest, Unrestored Interior
The cabin photographed for this gallery shows real wear consistent with decades on the road rather than a fresh restoration — a cracked dash pad along the windshield edge, a well-used black-and-red bench seat, and a period AM radio mounted low in the dash below the “PLYMOUTH” script badge. That kind of honest, driver-grade condition is common among surviving 1966 Belvederes, since most examples spent years as everyday transportation long before anyone thought to preserve them.
Plain Sheet Metal Hiding Serious Hardware
From the outside, nothing about this car’s black paint and simple trim gives away what a Street Hemi example carries underneath — no scoops, no special badging beyond what any Belvedere wore that year. That deliberate anonymity is exactly what made the 1966 Hemi Belvedere such an effective sleeper on the street, and it’s a large part of why so few casual observers today would guess this plain-looking coupe shares its engine with some of Chrysler’s most celebrated race cars.
A Steering Wheel Built for a Driver, Not a Cruiser
The wood-rimmed steering wheel and full round gauge cluster visible in these photos point to a car ordered with the console and gauge package rather than the base bench-seat, idiot-light dash most Belvederes left the factory with. Buyers who checked that box alongside the Hemi option were clearly building a driver’s car, not just chasing bragging rights over the engine choice alone.
Why the RH2 Body Code Matters to Collectors
The “RH2” designation in this gallery’s title refers to Chrysler’s internal body and trim code for the two-door hardtop Belvedere II, a detail that matters enormously to Mopar collectors trying to verify a car’s originality against its factory fender tag. Because so few 1966 Hemi Belvederes survive, matching the correct body code, trim level, and engine casting numbers is often the only way to separate a genuine numbers-matching example from a well-executed clone.
One Engine Option Among Five
It’s worth remembering the Belvedere’s engine lineup that year ran from a modest 273 V8 all the way up to the 426 Hemi, meaning most Belvederes built in 1966 left the factory with something far more ordinary under the hood than what this particular car carries. That spread mattered to Plymouth’s business — the Belvedere needed to work as affordable family transportation and as a genuine muscle car platform depending on which box a buyer checked, and the same basic sheet metal covered every version of that range.
A Reminder That Patina Has Its Own Story to Tell
The cracked dash and worn upholstery visible in these photos aren’t flaws to be apologized for — they’re evidence that this car actually did what Chrysler built it to do, carrying real owners on real errands for close to sixty years rather than sitting preserved in a climate-controlled garage. As unrestored survivors like this one become scarcer every year, that honest wear is increasingly treated by serious collectors as a feature worth documenting rather than a problem to be fixed before the next sale.
The Belvedere Name Outlived the Muscle Car Era
Plymouth kept the Belvedere nameplate in production through 1970 before folding it into the Satellite lineup entirely, meaning this 1966 example sits roughly in the middle of the name’s production run rather than near either end. That mid-run timing is part of why 1966 and 1967 Belvederes occupy such an interesting spot for collectors — late enough to carry the 426 Hemi option that helped define the muscle car era, but early enough to predate the flashier GTX and Road Runner badges that would eventually overshadow the plain Belvedere name on the very same chassis. These photos, courtesy of Gateway Classic Cars, capture that transitional moment well, right down to the plain black paint, the modest trim, and the well-worn cabin that together gave this quietly serious Hemi car its lasting sleeper reputation among Mopar enthusiasts.
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