392 Intake Manifold Development

Before the 392 engine went into production, in 2011, it was originally rumored to hit 500 horsepower. Kraig Courtney, SRT engine design supervisor, had addressed these rumors in Mopar magazine (March/April 2011), saying that they had improved the area under the torque curve at the expense of peak numbers:

"We were pretty confident that we could get 500 hp, but...the prototype 392 was strong up high, but as you accelerated, it didn't give you that kick in the butt we expected- a kick in the butt approaching that of the muscle cars of old...The first 6.4 just wasn't as strong feeling as the numbers said it should be. So we took a look at the intake that's being used in our trucks right now, it's an SRV dual-runner intake that we can run short runner or long runner. Obviously, you run short runner for power and long runner for torque. So we made up some manifolds and ran them in a car and it felt a lot better. Not as much horsepower, but the area under the torque curve was far bigger...We can go out and, quite honestly, take on some of the competition's cars that are more powerful according to their numbers."

Thus, the active manifold on the 392 Hemi allows it to be physically sized for optimal velocity for best low/midrange rpm performance, but still allows for free-breathing response on the top end, as the "active" gate opens up the short runner paths at upper rpm. As a result, the engine produces an impressive 485 hp. and 475 ft.-lbs. torque.

For more information about intake manifolds, see the following article:

Intake Manifolds | Dodge Challenger Forum