So I have a 1998 Silverado k1500, it has 102,765miles on the clock but I get terrible oil pressure. I’ve tested with a mechanical gauge and confirmed I get 25-27 psi at 3grand rpm and 5-8 psi at idle while the motor is at operating temp. So I’m wondering is it my oil pump or something else? The guy I bought it off of said he had redone the timing chain and tensioner along with the gears. So could that also be my issue? Any help is appreciated. There is also no knocking,or bad motor noise at all.
Your tests indicate that the bearings are worn. You can drop the pan/sump and take a look. Check the condition of the top end by performing a compression test.
You often have owners who are obsessed with changing the oil, forgetting about the oil filter.