Cam phasers are specially designed, computer-controlled cam gears that automatically optimize camshaft timing based on the current engine rpm. Currently they are used in all 2005 and newer Ford Modular 3 Valve and all 2007 and newer GM L92 engines. Engine oil is pressure fed to the cam phasers through a series of passageways in the cylinder heads and camshafts. The engine computers control solenoids that adjust this oil flow into and out of the phaser's control chambers, giving the ability to retard the cams up to 60 crank degrees.