Vanbcguy, That is what I was thinking, that there is a way to measure temperature or pressure off the oil flange but no actual valve. Never heard of anything that would sense oil temp and pass it through a heater like some auxiliary coolers do.
But I thought to mention the oil pump relief valve on the pump itself. Search this forum for dismantle, clean and repair of the pump relief valve. You might have a piece of something in there that is keep the full pressure from building up to where it should.