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So figured i'd put a few tidbits in here to share what I've learnt over the past 15 years
(background: drifting instructor for 4 years, owned an RB25 for 12 years with 38 events and unopened block/clutch/trans, pitcrew for 2x D1NZ teams)
One thing i've found with my engine and countless others I've worked on is that cooling (both water & oil) is critical.
First: oil
The first thing i always say to people running these engines is to get an oil temp & oil pressure gauge, preferably with warning lights. If oil temps go over 110 deg C then cool it down. Next step is an oil cooler with a fresh air feed, ideally in front of the intake-side wheel in behind a bashbar. You can go as far as i have and rig up water sprayers as well but that's up to you.
Yes RB engines don't let oil drain back down from the head very well, no denying that. They also tend to get a bit of blow by as they get old or as boost is bumped up. My engine compression tests up ~120psi cold across all 6, so the crankcase is getting a bit of blowby for sure.
Importantly in all this, all the factory crankcase pressure vents are only in the head. Unlike SR's, there is no breather coming from the block.
So the crankcase pressure is using the oil drains to evacuate via the vents in the cam covers. The oil pump keeps pumping oil up to the head, it can't drain back because the blowby is using the drains and you starve the bottom end of oil. Engine blown up, people get angry and don't bother to figure out why.
Solution: drill the block
We've found drilling the block where there are no oil galleries and venting it to a catch can remedied all problems. Oil temps dropped as more oil was returning to the pan faster. Things like rocker cover gaskets failed less as well as they are no longer seeing anywhere near as much pressure.
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