Go into the archives and find the articles about what happens if the rubber washers on the oil filter canister stalk are bad. I do not remember the exact details but worth checking out I believe. Simple stuff first. There is also a real long shot that the oil pressure sensor might have become defective after it gets hot but that is so long a shot almost to be nonexistant. Usually when an engines oil pressure goes to zero the top of the engine gets a little noisier. I would not count on that either with a 617 engine. It"s pretty noisey with oil pressure.