Muscle Cars You Should Know: ’67 HEMI Plymouth GTX “Silver Bullet”
For some Plymouth enthusiasts, the introduction of the 1967 Plymouth Belvedere GTX was a step down in the performance food chain. Still, in the continuing evolution of the marque’s muscle cars, the GTX held its own and led to an even greater competitor in the performance wars of the 1960’s.
As was the case for most intermediate-sized muscle cars, the cars they were based on were variations on products of modest pretension. First introduced in 1951, the Belvedere was a response to Chevrolet’s successful 1950 Bel Air two-door hardtop. The car enjoyed a great run through the fifties as a full size, full line model, including the 1956 introduction of the Fury as a special, hi-po model.
When downsized in 1962, general sales of the nameplate suffered, but the same year saw introduction of the big block 426cui V8 engine. The combination of lighter weight and more power made the Belvedere a highly sought-after model for drag racing. The evolution continued in 1964, when the 426 HEMI engine became available, leading to a 1-2-3 finish of the newly-restyled car at the Daytona 500 that year.
Other than discreet “HEMI” badges, 426-equipped Belvederes were the ultimate stealth car on the streets. A decision was made to build a performance image and so, for the 1967 model year, the Belvedere GTX was introduced. Available as either a two-door hardtop or convertible, the car came standard with a Super Commando 440cui V8 engine and TorqueFlite 3-speed automatic transmission. To help manage the additional power, the GTX was built with heavy-duty torsion bars, upgraded 6-leaf rear springs, over-sized anti-sway bars, heavy duty shock absorbers and uprated ball joints.
Promoted as The Gentleman’s Muscle Car, the GTX also received a special grille and tail panel, simulated hood scoops, a racing-style chrome gas cap, bucket seats, front and rear seat belts, and energy-absorbing steering column. Front disc brakes, and a four-speed manual transmission were optional.
The 440cui motor first appeared in 1966 for full-sized cars with 365 gross horsepower. Chrysler engineers prepared the engine for its debut in a mid-sized car by adding bigger valves in redesigned heads, along with extra-large throttle bores, a dual snorkel air cleaner, hot cam, over-sized ports and valves and cast headers. This jumped the output to 375hp.
Option for the 1967 GTX, the 426 “Street HEMI,” produced 425hp at 5000rpm and 490 ft-lb of torque at 4000rpm and was offered for a premium of $546 over the base cost of $3,178. Previously, the 426 HEMI was – in theory – optional across the line, and many 1966 buyers went for the HEMI in stripped-down bodies. To get the same engine in 1967, the buyer had to pay extra for the GTX trim.
Despite conceding 14cui to the standard engine, the HEMI left it behind, with its 50 additional hp – due to the special HEMI heads, higher compression ratio and dual 4-barrel carburetors. In performance comparisons, the HEMI would win a quarter mile fight. Typical performance for the 440 was 0-60 in 6.6 seconds and 1/4 mile in 15.2 sec at 97mph. For the 426 HEMI, the story was 0-60 in 4.8 seconds, 1/4 mile in 13.5 seconds at 105mph. However, since the 440’s torque peaked earlier and the HEMI had to wait until 4000rpm, and was harder to tune, races were often closely fought and a well-driven, well-tuned 440 car could beat a HEMI consistently.
Paying the premium for the GTX package ultimately resulted in a significant decline in HEMI car sales. In 1966, there were 1,510 HEMI-powered Belvederes built but, in 1967, that number fell. The easier-to-manage and much cheaper 440 V8 took away a lot of HEMI sales and in doing so made the 1967 Plymouth Belvedere GTX HEMI quite a rare example of the breed.
The performance story did not end there, however. Plymouth had quietly offered in the past, and continued in 1967, an R023 option, that was generally know of by professional racers only. Often called the “Super Stock” or lightweight version, this HEMI GTX was better known by what it didn’t have than what it did. A weight saving of several hundred pounds was achieved by eliminating the radio, heater, body insulation and sealers, carpet, underpad and even the hubcaps.
A large, functional hood scoop was about the only hint that this wasn’t anyone’s plain Belvedere. That hood scoop fed a cold air intake to the hand built HEMI engine, that came with a dual-point distributor, transistorized ignition, high performance ignition wires and dual Carter 4-barrel carburetors. Plymouth built only 55 R023 GTX’s, making them quite rare today.
The existence of the R023 package owes itself – at least in part – to an unassuming mechanic working at Ted Spehar’s Sunoco gas station on Woodward Avenue in Birmingham, Michigan. Jimmy Addison was known for his talent with Chrysler products, which was honed into an art as Addison had complete access to a vast array of exotic racing parts thanks to Spehar who made a decent business of building racing engines at his station. Spehar worked with Chrysler at the same time and saw an opportunity with Addison who was actively street racing a 426 Max Wedge ’62 Dodge.
Originally a Chrysler Engineering test mule, the HEMI Belvedere that would become the “Silver Bullet” wasn’t a silver HEMI car at all; rather, it was painted blue and equipped with a 375hp 440. Throughout the year, the Plymouth went through several cam, carb, intake, and header combinations for Chrysler’s factory racing department in Highland Park, Michigan. This “think tank” was helmed by veteran Bob Cahill, and staffed by Tom Hoover (who was instrumental in creating the 426 HEMI) and Dick Maxwell (who was a key member of the legendary Ramchargers racing team).
While street racing was not part of the “official” testing curriculum, stories began to swirl around the Auburn Hills central offices of a pair of older gentlemen campaigning a warmed-over Plymouth around the streets of Detroit. Of course, Chrysler wasn’t the only one using public roads and America’s youth as a marketing/test bed for their street performers. Pontiac, Ford and Chevrolet were all guilty of the same subterfuge, resulting in a swarm of factory-built GTOs, big block Mustangs and unmarked Chevelles cruising for a little action.
Through Spehar, the Plymouth was sold to Addison for $1, and under Chrysler’s guidance, the GTX was put on an extreme diet. Supplied with lightweight doors, a hood, window glass, front crossmember and bucket seats, Addison shaved off 500 pounds whittling the B-Body down to sub-3600 lbs. In addition to the drastic refitting, the 440 Wedge motor was swapped for a monster 487 cubic-inch HEMI with a 4.25-inch stroker crankshaft, oversize TRW pistons, a steep Racer Brown camshaft, a 10-quart oil pan and aluminum cylinder heads.
According to SilverBulletGTX.com, “Fuel was delivered to the twin Holley four-barrel carburetors via a Stewart Warner electric fuel pump, while Hooker headers directed exhaust to the four ’68 Cadillac mufflers through 3-inch pipes. Transfer of power to the M&H drag slicks at the rear was achieved with a modified Torqueflite automatic transmission, while compliant front shock absorbers teamed with super stock rear springs to achieve the desired rearward weight transfer.”
Repainted in bright silver paint, the “Silver Bullet” GTX was born. Even in full trim, the GTX ate up the quarter mile in 10.50 seconds at 132mph, and quickly became one of the most well-known and feared Mopars prowling Woodward Avenue.
Today, the “Silver Bullet” is owned by Harold Sullivan, a loyal Mopar collector who tracked the ‘Bullet down and restored it from a long life of hard knocks. Returned back from the brink of destruction, the original Silver Bullet runs and drives and can still light up the slicks. Yet, since Sullivan wanted to flog the ‘Bullet a little harder than he felt comfortable, Sullivan built another GTX in the “Silver Bullet II” which he races.
Plymouth muscle car history would continue to be written long after the Silver Bullet, but nearly no other street car played so part of that progression.
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