Introduced in 1967 as a more upscale alternative to the two-door Belvedere, the Plymouth GTX became known as “the gentleman’s muscle car.” It wasn’t exactly luxurious, but it offered more convenience features than the regular muscle car available at the time. And unlike the Belvedere, it was only available with Plymouth’s top-tier V8 engines.
Specifically, the GTX was equipped with the big 440-cubic-inch (7.2-liter) RB V8 as standard. The four-barrel mill was good for 375 horsepower, more than what a Ford Mustang Cobra Jet was capable of at the time. But Plymouth also dropped the awesome 426-cubic-inch (7.0-liter) HEMI V8 in the GTX. Rated at 425 horsepower, it barely had any rivals at the time.
The nameplate remained faithful to this lineup until it was phased out in 1971. That’s when Chrysler also discontinued the mighty 426 HEMI. However, Plymouth introduced a second 440 V8 for the 1970 model year. Yup, I’m talking about the six-barrel version of the mill that found its way in a long list of Mopars mid-way through 1969.
Rated 390 horsepower, it offered an extra 15 horses over the four-barrel 440. But it was more than just extra carbs. The bundle also included a unique intake setup, beefier connecting rods, valve springs lifted from the HEMI engine, and a compression ratio of 10.5:1.
Because it arrived at a time when high-performance cars were very expensive to insure, the 440-6 wasn’t exactly popular. Of the 7,141 GTXs sold in the U.S. in 1970, only 678 were ordered with the six-barrel mill. Yes, it’s nowhere near as rare as the HEMI variant, built in 71 examples, but that’s still less than 10% of total production. The same goes for 1971 when total GTX production dropped to 2,942 cars and only 135 of them got the 440-6 V8.
Come 2023 and these numbers are actually lower since many GTXs have been wrecked and abandoned in junkyards, so it’s not surprising that prices keep climbing into six-figure territory. So what do you do when you can’t afford a 440-6 GTX? Well, you can always restore a 440 car with a six-barrel mill under the hood. It’s been done quite a lot and the result is usually a really cool sleeper. This 1968 GTX is one of those cars.
But wait, wasn’t the 440-6 V8 introduced in 1969? Yes, that’s correct, but that didn’t stop Kevin Plummer from dropping a similar layout in an earlier Mopar. And based on the way it looks, that 440-6 is also more of an aftermarket effort rather than an all-original unit sourced from another Plymouth.
But it sounds just as cool as the real deal and I’d dare say it’s just as vicious as the 426 HEMI when the pedal hits the floor. But you don’t have to take my word for it. Hit the play button below to hear for yourself.
