The Performer RPM hydraulic roller cams feature more aggressive profiles without excessive valve overlap. The roller lifters reduce friction significantly and eliminate break-in problems. They also permit higher valve velocity, increasing performance while maintaining good manifold vacuum and drivability. These cams are for high performance street use only and are not for heavy vehicles. They should be used with or other aftermarket cylinder heads, adjustable valve train components and at last 9. 5: 1 compression ratio. Headers, high energy ignition systems, lower than stock rear end gearing and a high performance torque converter in automatic transmission equipped vehicles are necessary to gain all of the performance in these camshaft kits. In some designs the camshaft also drives the distributor and the oil and fuel pumps.