According to a recent report, Mercedes is developing a naturally-aspirated version of the twin-turbo 5.5-liter V8 used in the S63 AMG and CLS63 AMG.
Details are limited, but the new engine will reportedly produce 422 hp (315 kW / 428 PS) and feature multi-cylinder deactivation for improved fuel efficiency. While nothing is official, it is rumored to debut in the upcoming AMG variants of the SLK and C-Class Coupe.
Oddly enough, the C63 AMG sedan and estate will reportedly retain the 6.3-liter (6208cc) V8 with 451 hp (336 kW / 457 PS) and 443 lb-ft (600 Nm) of torque. Likewise, the Black Series Coupe will also use a modified version of this engine but previous rumors have suggested it will feature the twin-turbo 5.5-liter V8.