After extensive use in other models from the AMG division, there's not much reason to doubt Mercedes' claim that the 4.0-liter biturbo V8 in the AMG GT 4-Door Coupe 63S produces 630 hp. The same engine makes 577 hp in the basic 63 trim.

AMG keeps making tweaks to boost the output, and the new GT 4-Door Coupe is just the latest step in that development.