I've heard a lot of generalized statements about oil pressure that might make sense under specific circumstances. Most people get too concerned about specific numbers. It's normal for pressure to be high on a cold start and drop somewhat as the oil heats up and clearances expand. The most common complaint I hear that's totally untrue is "the oil pump failed" when people are describing a loss of oil pressure. In nearly 60 years of fixing cars, trucks, construction equipment, boats, and airplanes I've seen exactly three true oil pump failures. One pump sheared off the drive tangs because a piece of metal got between the gears through a hole in the pickup strainer screen and locked the gears. Two other pumps got the relief valve jammed open from foreign matter and although the gears continued to pump oil, the pressure went to zero and stayed there because all the output was being bypassed right back into the crankcase. Every other "pump failure" was actually worn out rod, main, or cam bearings, allowing more oil volume to leak away than the pump was able to supply. Panic makes a good point about the last bearing in the gallery being the one at the most danger. Like the last resistor in a series electrical circuit, there's not much "Voltage" (oil pressure) left to make the lube flow. I used to tap the pressure gauge line for the race car into the end of the oil gallery above the timing cover where they once attached the line for a remote oil filter on the 1955 small block 265 engines. That port was still being drilled and tapped as late as the early 327's and blocked off with a pipe plug. It was easy to drill the passage on a 350 and tap the hole for a 1/8" pipe fitting. That port monitored the oil pressure at the last possible source of pressure, furthest away from the oil pump.
Jerry
