sorry but this is totally wrong...
Simple. Some if not all RBs are known to starve oil. What happens is the oil in the head goes back to cyl 6 and 5 which starves the front I believe. That is why Carl H and many installed 2 lines in back of the head which leads to the oil pan so it can recirculate properly and efficiently. Also I think that there some oil slippage occurrence which leads to this problem as well. Its pretty common on GTRs.
the problem is the rb's oiling system is effcient but the drains in the head arnt large enough to return all the oil...so what happens is oil ends up pooling in the head instead of in the sump which can cause pressure fluxuations and/or oil starvation; typicaly this only happens at high rpm use like a track car or a hpde setup car...dont be fooled tho this can also happen to a dd.
to address this external drains are fitted to the head, and depending on which way you went this can be either 1 or 2 fittings leading back to the pan to help expidite oil return.
another way the oiling issue is addressed is thru fitting restrictors to the oil feeds for the head, sydneykid on skylines australia is well versed in tuning high performance rb motors and created a sort of 'spec sheet' for what restrictors to fit with what oil pump/motor combo.
now the last issue is the short snout oil drive on the crank, ALL rb20 motors, ALL r33 rb25 motors, SOME r32 rb26 motors suffer from this.
the issue is the drive for the oilpump is too short and at high rpms this can cause slippage and actualy destroy the oil pump gear resulting in instantatious low oil pressure and essensialy killing the motor.
the fix for this is to retrofit a redesigned pump to the motor (all rb motors use the same pump configuration) and fit a crank collar such as the jun, proengines, or gtr shop collar.
this involves removing the crank, having the snout turned down and the collar pressed into place, it is a friction fit with allen screws for safety.
thats the BASIC gist of the rb oiling issues, there are others but those are the major ones.
