long story: So I have a 4bt in a pettibone forklift that I got with a blown motor- #3 rod thru block due to runaway injection pump... I found a long block on ebay for $500. It looked like it had been rebuilt but had sat outside in water and had lots of rust damage. Cam looked brand new, so did rods and crank however on close inspection, #2,3 rods had spun bearings and rods had overheated in process. Ended up using ebay block, new cast crank (china), new head (Minnesota), two rods from blown motor, two from ebay motor, , new pistons +.010 (bored), oil pump from ebay motor (because it looked brand new), rebuilt injection pump, new turbo... Machine shop cleaned, bored, decked block, setup crank, rods, pistons. I assembled the engine put it back in machine. Machine had only oil pressure light. I installed gauge as well. Motor runs perfect. I have run it 4-5 hrs. It purrs like a kitten. Oil pressure is 10 psi at idle, comes to 30-35psi at speed. I have checked oil pump, oil pressure release, oil filter, oil cooler, plug in block at push rod cover. removed timing cover to look for gusher there. ran motor with timing cover off- no gushers there. removed oil cooler to check for flow/pressure from pump- It seems like there is good pressure there as I could not hold flow back with my thumb when cranking with starter. What to do? Should I just put the thing back together and run it? (The oil pressure light goes out) Where could I be losing oil pressure? Thanks for any advice.