In 2008, with the introduction of the 8.4 L V10, the Viper received a 90 hp (67 kW) bump up to 600 hp (450 kW), a 25 lb·ft (34 N·m) torque bump up to 560 lb·ft (759 N·m) and the engine displacement was increased up to 510.0 cubic inches (8,383 cc) from 505.6 CID (8,285 cc) of the 8.3 L engine, also receiving better flowing heads with larger valves, Mechadyne cam-in-cam variable valve timing on the exhaust cam lobes, and dual electronic throttle bodies. The rev limit was able to be increased by 300 rpm due to the improved valve-train stability from both the new camshaft profiles and valve-springs. The development of the engine was done with some external assistance from McLaren Automotive and Ricardo Consulting Engineers.