Regal V6-3.8L VIN K (1997)
Lifter / Lash Adjuster: Description and Operation
In addition to its normal function of a cam follower, each hydraulic valve lifter also serves as an automatic adjuster which maintains zero lash in the
valve train under all operating conditions. By eliminating all lash in the valve train and also providing a cushion of oil to absorb operating shocks, the
hydraulic valve lifter promotes quiet valve operation. It also eliminates the need for periodic valve adjustment in order to compensate for wear of parts.
Oil is supplied to the lifter through a hole in the side of the lifter body which indexes with a groove and a hole in the lifter plunger. Oil is then metered
past the oil metering valve in the lifter, through the push rods to the rocker arms. When the lifter begins to move up the cam lobe, the check ball is held
against its seat in the plunger by the check ball spring which traps the oil in the base of the lifter body below the plunger. The plunger and the lifter body
then raise as a unit, pushing up the push rod to open the valve. The force of the valve spring which is exerted on the plunger through the rocker arm and
push rod, causes a slight amount of leakage between the plunger and the lifter body. This leakage allows a slow escape of trapped oil in the base of the
lifter body. As the lifter rolls 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 check ball to open against the ball spring, and any oil inside the plunger is
drawn into the base of the lifter. This restores the lifter to the zero lash.
