This bullet-shaped plunger controls the amount of excess oil pressure dumped back to the sump. It can become lodged and damaged on the outside diameter and seating surface if debris has circulated in the engine. Inspect with every engine overhaul and replace if it shows marking. If it sticks open, too much oil can go to the sump and rob the engine of needed pressure. This plunger mates with 2A0797 seating, which is pressed into the block.