The camshaft is billet steel, made from 8620 carbon or S7 through-hardened tool steel or similar. It runs in five oil pressure lubricated bearing shells and is driven by gears in the front of the engine. Mechanical roller lifters (cam followers) ride atop the cam lobes and drive the steel push rods up into the steel rocker arms that actuate the valves. The rockers are of roller tip type on the intake and exhaust sides. Like the cam follower rollers, the steel tip roller rotates on a steel roller bearing and the steel rocker arms rotate on a pair of through-hardened tool steel shafts within bronze bushings. Intake and exhaust rockers are billet. The dual valve springs are of coaxial type and made out of titanium. Valve retainers are also made of titanium, as are the rocker covers.