When I had fitted the RB25DE, bought from a wrecker and been sitting there for who knows how many years, first thing I wanted to see was oil pressure. Cranked the engine with no plugs to make it easier on the starter and battery and also spin the engine a tad quicker. Since the oil pump was dry, I got no pressure at all even after a few attempts so had to get compressed air into the rocker cover breather with the oil filter off and blocked off any other hole to keep the block sealed to build pressure up. Once the engine was cranking, forced air into the block, before you knew it, liters of oil came gushing out of the oil filter mount! Re-installed the filter, cranked the engine again, hello oil pressure gauge movement! Then powered up fuel pumps, ignition etc, engine came to life! Oh, make sure you have plenty of water in the cooling system and fresh clean oil. And a can of "Aerostart" to spray in the carbs when you are ready to start!