V90 L6-2.9L VIN 96 B6304S (1998)
Lifter / Lash Adjuster: Description and Operation
DESCRIPTION
The valves are operated by twin overhead camshafts through hydraulic tappets (or valve lifters). The oil-filled tappets are self-adjusting.
OPERATION
Each tappet is held in contact with the camshaft by a spring in the tappet cylinder. The spring force is lower than that of the valve spring to ensure that
the valve is free to expand linearly.
A non-return valve prevents the escape of oil when the camshaft is operating the tappet, and when the oil pressure in the tappet cylinder is higher than
the engine oil pressure
Tappet In Contact With Base Circle Of Cam
Oil from the channels cast in the underside of the upper cylinder head is forced into the tappet through a groove and a series of holes in the side,
entering the plunger through a slot in the top. Since the engine oil pressure is higher than that in the tappet cylinder when the tappet is not being
operated by the cam, the oil flows through the non-return valve into the tappet cylinder.
Tappet Operated By Cam
When the tappet is pressed downwards. the oil pressure in the tappet cylinder exceeds the engine oil pressure. closing the non return valve and
effectively making the assembly a solid component.