93 with Knock Help Please

heya Ya'll
I have a 1993 silverado with a 5.7 v8 in it with 238k on it. My question is this. When I start the motor cold I get the typical piston slap noise that goes away immediatly. Then the motor runs great with about 60psi pressure. After the motor starts warming up and especially after being at operating temp for a while, the pressure drop to 30 max, and even will flutter between 10 and 0 (with warning gauge fluttering) at a stop. Also at a stop it'll start knocking. Not super loud but definatly enough to hear it. Any ideas what is wrong with this motor? are both symptoms related? Thanks for any help!


Act

I would get the oil pressure checked with a mechanical gage to confirm these readings, if they are right, off comes the pan for bearing inspections.

Another good way to check it is to pull of the oil filter, cut it, and check it for bearings.