When installing a new replacement cylinder block/engine in a Nissan 300 ZX non-turbo car equipped with the 3.0L VG30 engine you’ll notice the new block/engine assembly comes with two blind plugs installed in the oil filter bracket boss on the engine block. The original engine that is removed from the vehicle has two oil pressure regulators installed. The blind plugs must be removed and the regulator valves installed to prevent engine damage. Drill, thread and use a slide hammer to remove the blind plugs.
During the engine rebuilding process all of the cylinder block plugs/oil pressure regulators get removed, so the block can be cleaned. See Figure 1, for the correct location of the oil pressure regulator valves. Nissan part number for the oil pressure regulator valve is p/n 15241-40F00 (two are required). Drive in the new oil pressure regulator with a suitable tool/socket just flush with the mounting surface.
NOTE: The 300 ZX Turbo engine has the oil pressure regulator valves installed in the oil filter bracket and does not need this procedure.