My problem started with a main bearing that needed replaced and through the process I replaced alot of parts. New crankshaft, piston rings, heads, all gaskets, oil pump (gears), water pump, spark pugs and wires, oil pressure sensor, new oil and filter. Too much $. Now she’ll start and run good, except the oil pressure. At the initial start it will be around 60 or a little lower but after the car warms up it will drop to 35 or so. If you drive for 30-45 min the oil pressure will read in the red 0. Also when I sit at a stop light she’ll act like she wants to die but won’t. We have checked over everything. Could it be a wrong crankshaft meaning not enough clearance, or the piston rings, or maybe timing? The big issue is the oil pressure. We’ve had to pull this engine apart a couple times and are getting tired of it. We are doing the work our self. If you have any suggestions, please let me know. I know its hard without actually seeing the car or hearing it but anythings worth a try.