The oil pump seems to be one of the few short-comings of the Nissan RB-series engines. I'm led to believe that the securing bolts tend to work loose (from heat / cool cylcing), then oil can be pumped out the gap, so not all the oil lubricates the engine. [/b]
Yep this is exactly what happened to my mates rb20. The securing bolts worked loose , had no oil pressure, engine died.