page_title: Tappet
section_title: Internal combustion engines
hierarchical_section_title: Tappet / Internal combustion engines
caption_attribution_description: Pushrod valvetrain
context_page_description: A tappet is most commonly a component in an internal combustion engine which converts the rotating motion of the camshaft into linear motion of the valves, either directly or indirectly.
  An earlier use of the term was for part of the valve gear in Beam engines beginning in 1715. The term is also used for components in pneumatic cylinders and weaving loom.
context_section_description: In an internal combustion engine, a tappet (also called a 'valve lifter' or 'cam follower') is the component which converts the rotation of the camshaft into vertical motion which opens and closes the intake or exhaust valve. The types of valve lifters (i.e. tappets) commonly used by automotive engines are solid lifters, hydraulic lifters and roller lifters.
  An alternative to the tappet is the 'finger follower', which is a pivoting beam that is used to convert the camshaft rotation into opening and closing of a valve. Finger followers are used in some high-performance dual overhead camshaft engines (instead of bucket tappets), most commonly in motorcycles and sports cars.
  To reduce wear from the rotating camshaft, the tappets were usually circular and allowed, or even encouraged, to rotate. This avoided grooves developing from the same point of the tappet always running on the same point of the camshaft. However, in some relatively small engines with many cylinders (such as the Daimler '250' V8 engine), the tappets were small and non-rotating. 
  Most 'flat' tappets (i.e. without rollers) usually contain a slight radius which creates a subtle mushroom-shaped surface, since a perfectly flat surface leads to 'slamming' against a steep camshaft face.
caption: Overhead valves and their actuation mechanism. Camshaft is to the far right, and the tappets are next to it
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