These Guys Turned A Crate Demon Hemi Into A 1,400-HP Supercharged Monster

In stock form, Mopar's Demon Hemi crate engine makes a healthy 807 horsepower and 717 pound-feet of torque. To be clear, this approximately $21,000, 6.2-liter, over-the-counter crate engine is technically called the Hellcrate Redeye Supercharged Hemi. But rest assured it's the same exact powerplant found in the Dodge Challenger SRT Demon (though not the gonzo Challenger SRT Demon 170 street racer), hence the Demon crate engine moniker. However, for one owner of a highly customized Jeep-style truck, apparently 807 horsepower just isn't enough.

Now granted, this Demon crate engine needed a rebuild anyway. Tim Eichorn, owner of MPR Racing Engines in Florida, gave more information to Engine Builder Magazine. "It came in with a few melted pistons," Eichorn said. "The tuning and fuel system just weren't where they needed to be –- too much timing, not enough fuel. In a one-off conversion like this, the supporting systems are often an afterthought, and it caught up to them."

Instead of nursing the supercharged Hemi back to stock specs, MPR threw an entire catalog full of high-performance goodies at the wounded long block. To start, a stroker crankshaft from Manley increases the engine's displacement from the factory 6.2 liters by an unspecified amount. A set of CP forged pistons replaces the damaged stockers and they're attached to the crank with beefy Manley H-beam connecting rods. That's all well and good, but it's in the blower department where things really get interesting.

The factory Demon supercharger (featured above) is a fine unit and can even serve as a low-buck path to boosting your Chevy LS. However, when four-figure horsepower is your goal, it's time to go aftermarket. In this case, a larger displacement blower from Whipple is the weapon of choice. Of course, changing the displacement of the Demon crate engine as well its boost capability requires a reset in the valve timing department and a custom ground camshaft from Comp Cams was selected to be the brains behind that operation.

At the risk of going down a technical rabbit hole, we won't list every single component used to increase this mill's horsepower by over 50%, but it's worth mentioning that MPR Racing Engine's attention to detail is a big part of the equation. This Demon Hemi underwent a rigorous CNC machining process to ensure the block and cylinder bores are straight and true. 

Once all of the tuning is complete, this mill is expected to reliably make 1,300 to 1,400 horsepower on premium pump gas. That's enough horsepower to run in the 8-second range at your favorite quarter mile drag strip. That said, this engine is going right back into its old home in a show-quality street truck which probably won't see many — or any — quarter mile passes. But what the heck? It's only money.