AUBURN HILLS, MI – An engine that almost never stops consuming fuel while generating 707 hp in the 2-door Dodge Challenger SRT Hellcat and the 4-door Charger creates extreme internal loads that can cause catastrophic failures if not offset properly.

Bulkheads in the block needed stiffening. Additional cooling was vital. Alloy pistons had to be forged (like those of the SRT Viper) for additional strength rather than cast. Fuel lines needed to be bigger. Crushed diamonds were embedded in steel washers to deliver the necessary friction to power the supercharger.

It’s because of this painstaking attention to detail that Chris Cowland, Chrysler’s director-Advanced and SRT Powertrain, grows prickly when defending the validity of the horsepower and 650 lb.-ft. (881 Nm) torque rating.

“If you see any of this crap in the press that it’s not a 707-hp engine, it’s absolutely untrue,” he says. “SAE (officials) were here; they witnessed it. No one should be doubting that’s the real number.”

Most blocks for new engine programs today are made of aluminum. The Hellcat, which is machined and built in Saltillo, Mexico, requires cast iron.

“It’s important to keep the bores as round and cylindrical as we can, and an iron block really helps in that respect,” Cowland tells journalists during a Hellcat deep dive here.

“If we switched from iron to aluminum, we couldn’t get the bulkhead stiffness we need under those firing loads,” he says.

“Of course, we can redesign the engine to run under aluminum, but we would have to spread the bore centers and would have to change lots of things within the engine. We always started this program with the premise that we wanted it to be based on the Hemi architecture.”