The 426 cubic-inch Hemi V8. Few engines in the world have such a storied history and devoted following. It’s even more impressive when you consider this engine – in 426 cubic-inch displacement anyway – has been out of production for nearly 50 years. 1971 was the last year Chrysler offered a factory-built 426 Hemi in a street car, and technically speaking, modern-day Fiat Chrylser Automobiles still doesn’t offer the 426 in something you can buy from a dealership.
However, the automaker does have a bonkers 426 Hemi crate engine available. We’re sure you remember FCA’s Mopar team announcing the 426 Hellephant back in 2018 during the SEMA Show. The folks at Demonology certainly remember, as they acquired one of the rare engines and dropped it into a Challenger SRT Demon. After all, why settle for a mere 840 horsepower when you can have 1,000? Does it really develop 1,000 hp though? That's right, it's time for another round of is this engine underrated from the factory? Spoiler alert – it could be, but we're lacking context to say for sure.
FCA’s official rating for this engine is 1,000 hp, and since this is a crate engine without a specific vehicle to call home, that figure is obviously measured at the crankshaft. With the mill stuffed into the engine bay of this Demon, Demonology makes a chassis dyno pull that returns 944 hp to the wheels. Assuming 15 percent driveline loss going through the Demon’s automatic transmission, that means the Hellephant here is making not 1,000 hp, but 1,110 – a full 110 more than FCA claims. That’s not slightly underrated, that’s in a completely different universe of horsepower.
Gallery: Dodge Challenger Demon Hellephant Swap
However, we’d be remiss if we didn’t point out several caveats to this particular video that could affect that figure. By now, you should know that not all chassis dynos are equal. Different brands produce different results, and though there are calculations and formulas that can level the playing field, at the end of the day they are just estimations. For that matter, stand-alone dyno figures are generated based on calculations derived from human input, and as we saw last year with Motor Trend’s C8 Corvette dyno fiasco, small input errors can lead to big mistakes.
We also don’t know for sure this engine is, in fact, straight-from-the-crate stock. It's assumed to be, but the video description or the clip itself offers no specific insight aside from the car running an E-40 fuel mix. Beyond that, variables such as temperature, humidity, and obviously altitude can affect engine performance. Lastly, there’s the possibility that the Demon’s driveline loss is less than 15 percent.
At the end of the day, all the variables are a moot point. This engine is supremely powerful, and with a price of $30,000, it’s also supremely expensive. Is it worth the cost to have a proper 426 Hemi under the hood, even if it only makes its advertised 1,000 hp?