Good afternoon everyone! I have a 2003 yukon Denali with a troublesome 6.0L and I need some ideas. I rebuild the engine after I blew a head gasket and noticed some scoring on the cylinder walls. (The engine was slowly losing oil pressure before the rebuild). With the new rebuilt engine in I am only starting with 35psi of oil pressure and it continues to drop as the engine warms up. By the time the engine is at operating temp it is down to 5psi. Is it possible an O-ring is bad? I just wanted some ideas before I start tearing into it again.