Hellephant-powered 1968 Road Runner is a 1000-hp sleeper done right

You’d be wise to not underestimate a ’68 Road Runner, even one with a tame, quiet idle. However, you certainly wouldn’t expect even a potent muscle car engine of the era to be capable of producing 1000 hp without a rough, staccato idle that would announce its presence from a block away. Don’t be fooled. This blue-on-blue 1968 Plymouth, looking every bit like a restored show car, is packing 426 cubic inches of Gen III Hellephant crate engine under its hood. It’s slated to cross the auction blocks at Mecum’s Kissimmee, Florida, sale in January 2024.

For some Mopar fans, the thought of a 426 Hemi conjures up images of E-bodies with shaker hood scoops, or perhaps a lightweight 1968 Barracuda prepped for drag racing. For us, it’s the Dodge and Plymouth B-body that is most synonymous with the V-8 Elephant that became such a revered engine on streets, dragstrips, and on NASCAR’s superspeedways.

The magical 426 cubic-inch displacement is synonymous with the Gen II Hemi of the muscle car era, but there’s also an impressive late-model crate engine that took a different approach to getting that kind of displacement. Just 100 Hellephant crate engines were built at sold by Mopar, and the recipe for their ground-pounding 1000 hp and 950 lb-ft of torque was an aluminum Gen III Hemi block—all production cars and trucks sold with at Gen III Hemi used iron blocks—with a 4.125-inch bore and a 4.0-inch stroke. Like the Hellcat V-8 that it was developed from, the Hellephant’s aluminum heads were topped by a sizable supercharger and charge cooler. In retrospect, this engine was likely the beneficiary of a lot of the engine development that went into the 1025 hp, 6.2-liter Hemi that powered the Demon 170.

When Mopar first showed the Hellphant crate engine at SEMA 2018, we were hoping for builds like this, although we didn’t expect a builder to start with an already restored beauty. Before its transformation, this Road Runner was a hit at the Muscle Car & Corvette Nationals, where it scored 990 out of a possible 1000 points thanks to an incredibly detailed restoration that retained the factory interior. Its original four-barrel 383 engine was rated at 335 hp and the big bore, short-deck big-block was capable of much more. However, the 1968 Road Runner was also available with the legendary 426 Hemi, so perhaps this well-muscled coupe, even in its restored glory, always had a chip on its shoulder. Not anymore.

Aside from its monster motor, the Road Runner also received a set of subframe connectors to help the body keep up under the strain of 950 lb-ft of torque. Inside, the otherwise original interior was upgraded with a Vintage Air air conditioning system and what looks like a Dakota Digital dash to help keep tabs on the V-8. The dash blends in nicely and still uses three 180-degree-sweep analog gauges on either side of a small display. The factory floor shifter, once connected to a four-speed manual transmission, is now a Lokar piece that shifts a GM 4L80E. The four-speed automatic trans is a popular choice for high-powered drag-and-drive cars and is known for being able to stand up to lots of torque while letting big engines loaf around at highway speeds thanks to its 0.75:1 overdrive.

We’ll be watching this auction at next month’s Mecum sale, as we’re interested to see how collectors respond to a well-restored car going under the knife to accept a modern powerplant. If there was a modern engine worth dropping into such a classic, it would have to be the Hellephant.

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