Hydraulic Valve Tappets
WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 2003 Ford Pickup, 2003 Ford F550 Super Duty, 2003 Ford F450 Super Duty, 2003 Ford Excursion, and 2003 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
The hydraulic valve tappets minimize engine noise by maintaining zero valve lash. The hydraulic valve tappets incorporate camshaft follower guides and a roller follower design that reduces camshaft wear.