I have a very high mileage 5.3l out of a 2000 gmc swapped in my truck, and i'm only reading 16-18 psi at idle and it never gets above 35-40 even at WOT. My moms van with a 5.3 reads atleast 40 at idle and my buddies lq9 reads 40 too. After my 5.3's ran for 10 min it gets a wicked lifter tick. I'm running castrol gtx high mileage 5w-30. Oil pump giving up? would replacing the pump fix it? Would running thicker oil at least band aid the issue until i have more money to get another short/longblock? next oil change i'm going to sea foam EVERYTHING to see if it's just clogged up with sludge from being 13 years old and having 200k miles.

 

try a new pump

 

i would, but it's my DD and i'm the brokest 16 year old ever. "trying" a new pump is a big risk of time and money for me. i would like to atleast be pretty sure it would solve it, and if i would be better off saving up for a new longblock

 

I had the same issue with mine reading 40psi cold @idle then 20psi hot. I switched to a K&N oil filter part# 1017 and used 10w40 castrol GTX. Idles at 50psi cold and goes no less than 40psi hot. If I step on it it shoots to 70-75psi