Beretta V6-191 3.1L (1990)
Lifter / Lash Adjuster: Description and Operation
Valve Lifter Operation
Oil is supplied to the lifter through a hole in the side of the lifter body which indexes with a groove and hole in the lifter plunger. Oil is then metered
past the oil metering valve in the lifter, through the pushrods to the rocker arms.
When the lifter begins to slide up the cam lobe, the ball check is held a against its seat in the plunger by the ball check spring which traps the oil in the
base of the lifter body below the plunger. The plunger and lifter body then raise as a unit, pushing up the pushrod to open the valve. The force of the
valve spring which is exerted on the plunger through the rocker arm and pushrod causes a slight amount of leakage between the plunger and lifter
body.
This "leak-down" allows a slow escape of trapped oil in the base of the lifter body. As the lifter slides down the other side of the cam lobe and reaches
the base circle or "valve closed" position, the plunger spring quickly moves the plunger back up) to its original position. This movement causes the
ball check to open against the ball spring and oil from within the plunger is drawn into the base of the lifter. This restores the lifter to zero lash.
