Chain drive bolt-in cams. No headwork required. Lift designed for stock valve springs. Works well at 9.0 to 10.1 compression. A very effective combination with flattop pistons and stock, or slightly modified, heads. A noticeable increase in power and torque. This cam has a broad torque band that will start at 2000 RPM and still pull through the higher RPM range. The 510 is available for 99-06 models and the 555 is available for 07-present motors, only for chain drive.