What is 440+6?
An engine produced by the Chrysler Corp. in the late '60s and early '70s. Chrysler took their 440 cubic inch motor and swapped the 1 four-barrel Carter carburetor with 3 two-barrel Holley carbs which became collectively known as the "six pack". Other upgrades were also made to the motor. The engine was officially rated at 390 bhp/490 lb-ft. but, like many other big block engines of the time, it was underrated. It was featured in the Road Runner, GTX, Superbird, Super Bee, Coronet, Charger, 'Cuda, and Challenger.
That 440+6 Road Runner just ate that Hemi 'Cuda up for dinner.