Hydraulic tappet ?

dawudih

The image above labels the bucket as a valve lifter. Since there is a bucket there, there will be a shim beneath it. This means the valvetrain will need adjustment, by changing the shims out to thicker/thinner ones, periodically (15k on motorcycles is the new standard). There is also no traditional cam shaft, but a series of levers to control the lift & duration of the intake valve. This is a high performance set-up normally not used on street cars.