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Plymouth GTX: high-trim muscle, 1967 to 1971

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Based on stories by Jeremy
and Lanny Knutson of the
Plymouth Bulletin

In 1967, the mid-sized Plymouth Belvedere gained a new trim line: the GTX 440, the "gentleman's muscle car" (along with the 300 letter cars).

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The GTX was created in reply to questions used by people like Hot Rod's Eric Dahlstrom: "How will you tell it's a Hemi?" The most powerful engine to come out of Detroit in 1966, the Street Hemi was installed in cars that, except for discrete "HEMI" badges, looked no different from those powered by 318s and slant sixes. "It pays to advertise," claimed Dahlstrom, and that's what Plymouth did for '67.

The two-door hardtop body was outfitted with fiberglass simulated
hood scoops and optional racing stripes, a blacked out grille and on the
rear fender a racing style pop open gas cap. Inside was a 150 mph speedometer
and optional electric tachometer mounted out of the way on
the optional center console.

Plymouth designer/stylist John Samsen wrote, "At the time we designed these cars [1964 to 1966 Fury and Belvedere], the guidance from Sales was to make the cars look as wide as possible, front and rear. Quad lamps were mandated on all but the A body cars at that time. Being smaller than standard lamps, they were easier to fit into the grilles."

Standard features included the 440 Super Commando engine, bucket seats, Charger-like "pit stop gas cap," and front and rear seat belts; options included front disc brakes, a four-speed manual transmission, and (apparently hard to keep in original condition) wooden steering wheel. As with all Plymouth cars, the front suspension relied on torsion bars and an anti-sway bar, while the rear suspension used on leaf springs; but the torsion bars were heavier duty than standard models, with oversized anti-sway bars, heavier duty leaf springs, and the beefed-up 727 TorqueFlite automatic transmission.

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The GTX came with a standard 365-horsepower (gross) 440, which had been brought out in 1966 for full-sized cars. For the 1967 cars, Chrysler adding ten horsepower by putting bigger valves into redesigned heads. It came with extra-large throttle bores, dual snorkel air cleaner, hot cam, oversized ports and valves, and cast headers.

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The optional engine was 14 cubic inches smaller, but with its legendary Hemi heads and slightly higher compression ratio, the 426 Hemi produced 50 more horsepower. It was less "streetable," though - requiring more maintenance and driving skill - and a hunk of cash as well. 14 Hemis were installed in convertibles, the rest in hardtops (48 Torqueflites; 60 four speeds).

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On all Plymouths, the Hemi got a 3.23:1 axle ratio with the automatic; a manual transmission required the Sure-Grip differential (optional with automatic), and came with a 3.55:1 rear axle ratio. The 440 had the same axle ratios, with an optional 2.94:1 with the automatic (but no Sure-Grip axle). These were not unusual ratios.

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1967 GTX Car of the Month

1967 Belvederes, including the GTX, had dual hydraulic braking, with one system for the front and another for the rear; front disc brakes were optional. The GTX had bigger drums than the Belvedere: 11 by 3 inches, with 11 x 2.5 in the back - and wider wheels (5.5 inches which was also the case for wagons, towing packages, and any car with a Hemi.) Tires were 7.75 x 14 Red Streaks.

The GTX shared most Belvedere dimensions.

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The car magazines enjoyed speculating whether the cubic inches or head design would carry the day; in general, the Hemi would win the quarter mile, but since the 440's torque peaked at 3200 rpm while the Hemi had to wait until it reached 4000, and was harder to tune, a race was often tight. Well-driven, well-tuned 440 cars could beat Hemi cars.

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Of the various Plymouths, only the GTX had the Hemi in model-year 1967; in 1966, it had been optional across the line, in theory, and many 1966 buyers went for the Hemi in stripped-down bodies. To get the same engine in 1967, the buyer had to pay for the fancy GTX trim, leaving many "little guys" out in the cold. The result of that was a decline in Hemi car sales, from 1,510 Hemi-powered Belvederes made in 1966, to 125 were produced in 1967. The cheaper 440 took away some Hemi sales; Plymouth would address the "budget body" problem with a vengeance in 1968. ("Beep-Beep!")

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In 1968, the line was dramatically restyled, with more curved surfaces, fewer sharp angles, and a generally more finished look; it extended to every part of the car, including the roofline, which resembled that of the (also restyled) Dodge Charger. The sides had "Coke bottle" styling, not quite as extensive as that of the Charger.

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Despite these changes, U.S. GTX sales only hit 18,940 cars, mainly hardtops (convertibles sold slowly); yet, it was the best sales the GTX would ever achieve, given competition from the beautiful new 1968 Dodge Charger (not to mention the far cheaper 1968 Road Runner. The Road Runner had tremendous acceleration and strong cornering, but without the luxuries of the GTX - or its high price; while the GTX started at $3,329, the Road Runner started at $2,870 with its base four-barrel 383).

The formula used by the 300 letter cars and Imperials had not been entirely sound - many buyers wanted the performance but not the other goodies (and, of course, Plymouth usually did not command a high price). The Road Runner outsold the GTX by more than two to one in 1968; within the Road Runner line, the cheaper coupe outsold the hardtop two to one. Road Runners were around a hundred pounds lighter than the GTX, helping their speed, and came with a more "fun" appearance package.

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The 1969 Plymouth GTX gained an optional cold-air induction package, using hood scoops; it had a new grille and rear styling. To get from Road Runner to GTX meant adding a heavy duty battery, altered exhaust, stripes, hood scoops, bucket seats, vinyl trim, heavy duty suspension, deep-loop carpeting, numerous trim pieces, and the standard 440 with performance cam and bigger valves and ports (rather than a 383). Still, just 15,602 would leave American dealerships in 1969. Road Runner was outselling GTX by a factor of five to one, with a base price of $2,945 to GTX's $3,416.

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The 1970 Plymouth GTX's grille, hood, fenders, and rear panel were all changed from 1969; the price went up to $3,535, and the slow-selling convertible (just 700 were made in 1969) was no longer available.

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1971 was the last year for the GTX as a separate model; it had outlasted the Belvedere itself (the car had been renamed to "Satellite"), despite its slow sales. Plymouth moved over 66,000 Satellites and over 150,000 Fury IIIs, more than all the big Plymouth muscle cars combined, compared with 24,000 Belvederes the year before. The big hit, the new Plymouth Duster, made all the other cars look unpopular, with nearly 200,000 made in 1970 alone.

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The 1971 GTX brought in a hefty body-style change, a continuation of the "fuselage" style; aircraft and space motivated, John E. Herlitz's groundbreaking styling featured swoopy lines, and large, looping bumper/grill assemblies. One of the more functional changes was the extension of the rear track by nearly three inches, improving cornering. Other changes included new interiors, sunroofs, flush door handles, ventless side glass, functional air-grabber hoods, and the famous Tuff steering wheels.

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Inside the GTX, contour bucket seats became standard. The Tuff steering wheel was a mere 14.5 inches in diameter but a full inch thick. Rear spoilers were optional, along with rear window louvers. Wheels expanded to 14 x 6, with optional 15 x 7 rims.

The wheelbase dropped an inch, to 115 inches; length was 203.2, height 53.0, width 79.1, and maximum track 62 inches. The front torsion bar had a .92 inch diameter; the front stabilizer bar had a .88 inch diamter. In back, the left side leaf springs had five leaves and two half-leaves; the right side had six leaves.

The 440 put out 370 gross horsepower - measured as net, it was 305 - at 4,600 rpm; torque was 480 lb-ft at 3,200 gross, 400 net (net horsepower was measured with all engine accessories in place). The standard rear axle had an 8 3/4 inch ring gear diameter and a 3.23:1 ratio.

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The 1971 GTX, in its fourth and final year as a "model" rather than a trim level or option package, hit just 2,942 sales in the United States - making the 1970 GTX sales seem downright positive. In contrast, Duster continued to soar with over 185,000 sales, showing that price does matter, at least for value brands.

Patrick Drake wrote: I bought my 1971 GTX new from a dealer in La Puente, California; it had been built at the L.A. assembly plant in September 1970, the last 440 vehicle sold in California (I had dealers check for any available). It competed at Lions drag strip and Orange County International for a couple of years before I moved back to Canada. In 1986 it came in second in bracket #2 at the U.S. Mopar Nationals. It now has 70,000 miles, and the engine is original and as strong as ever.

Instead of a GTX, Plymouth sold a 1972 Road Runner with the 440-4 engine in 1972-1974, an option formerly reserved for the GTX. We have not been able to verify this sentence: The GTX package then included the 440 engine, heavier torsion bars (0.92" diameter instead of 0.88"), and three GTX emblems - one for each fender, and one on the trunk next to the "bird-in-circle" decal.

Engines were essentially the same as in 1971, except for the use of electronic ignition; horsepower ratings fell as the switch from gross to net was made universal and gross figures were no longer reported. Sales fell for 1972, partly on misunderstanding of the rating system, but went back up (though not up to 1971 levels) for 1973 and 1974. (Thanks, Dave Wilson.)

The 1972 model year was the last one for the 440 Six Pack; John Shoe wrote that they ceased production late in calendar-year 1971.

The Road Runner fell from its strong prior sales to a meager 7,628 cars made - an astounding drop (the Duster exceeded 212,000). If the GTX existed at all, and it was not in the Plymouth brochures we’ve seen except one note about a “GTX engine” which may have been an error, sales were not broken out separately.

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Though not many people bought a Plymouth GTX, it remains a staple of car shows, and was moderately popular in movies, featured in Brewster McCloud, Fifty-Two Pickup, Joe Dirt, Tommy Boy, and the 1999-2004 TV series Angel.

Edited by David Zatz - January 18, 2021


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