Wow, it really does seem that you have an oil pressure problem, I also have a BBC in my jet boat built by me, I too have a Dooley 10qt pan, but only use 9 qts. I run a Melling HV pump with a GM factory windage tray. I use Valvoline 20w-50 VR1 oil and upon start up there is 80psi and even when oil temp is 180* cruising at 3,000rpm I have around 60psi and 35 psi at 950 idle rpm. So I would have to say it’s an internal issue with a clearance problem or an early bleed off some ware. The Chevrolet engine’s oiling system is quite simple and reliable, there is no way 20psi is normal or acceptable. Over my years I’ve seen some weird things that could affect oil pressure, extremely worn out cam bearings is one of them, causing an early bleed off before oil gets to the mains and rod bearings. Oil pump issues with the spring or bypass valve, but that’s kinda rare, but look over that pump closely, mating surfaces too on that 5th main cap, torque specs and pick up. I really don’t feel you need any specialty items like a crank scraper, those items are above our performance level to see any gains, you have a legitimate problem that needs to be found before damage occurs. I’ve even seen an internal crack in a block that when it heats up and oil thins down the pressure would really drop, just a few ideas, but my honest opinion is that I’m thinking that engine needs to be looked into closely to find the culprit, perhaps get with your engine builder and discuss options.
