Abstract: A hydraulic tappet for an internal combustion engine has a collar located axially on a valve stem, the outer periphery of the collar slidably engaging a cylindrical bore which is coaxial with the valve stem. A cap having a central tubular formation which slidingly engages over the end of the valve stem and an outer periphery which engages the cylindrical bore, is separated axially of the collar, to define a first chamber between the cap and collar and a second chamber between the cap and the end of valve stem. An inlet for hydraulic fluid is provided to the first chamber and the first and second chambers one interconnected by a non-return valve which prevents flow from the second chamber. A controlled leakage path is provided from the second chamber and a spring biases the cap into engagement with a cam formation.

Abstract: A balancer has a pair of shafts disposed parallel to one another and being adapted to be driven at the same speed in opposite directions, each shaft has a pair of axially separated weights mounted thereon, all four weights being of equal mass. The weights on each shaft are disposed at different angular positions, the disposition of weights on one shaft being the same as that on the other shaft, each weight on one shaft being disposed at 180.degree. to the corresponding weight on the other shaft when the centers of mass of the weights are disposed in the common axial plane of the shafts.