68shortfleet

I am having a strange oil pressure issue that I am hoping I could get some advise on.
Background info: This is a swap into a 68 C10 SWB.
Engine block is a LM4(2004 trailblazer ext) that has been bored to 5.7(3.898). And an LS6 5308 cam installed. Also has a ported GM performance oil pump in it. Motor has less than 1500 miles on it. Basically everything was replaced except the cam bearings.

On cold startup I have excellent oil pressure 45psi at idle with a steady needle. And after the engine warms if I still have 20+psi at idle. These readings taken from the top of the block at the stock oil sender location with a mechanical guage. This is NOT the faulty sending unit issue that seems to plague the F bodies.

However, I will sometimes get a unsteady reading. Shown in this video.


Anybody have any suggestions?

nine8ss

iTrader: (5)

My oil pressure gauge reads the same way. Will hold steady at 40-45 on cold start and once warmed up, reads around 28-30 with the slight fluctuation that you show. New oil pump and OPSU and the issue remains.

OwieVT

Your pressure values are lower than mine but I think yours still fall in the typical range. I have a 1999 LS1 with 200k and I use Valvoline 5W-30 full synthetic and mine is 55-60 at cold start-up and it stays at ~40 when hot regardless of rpm.

68shortfleet

I guess my concern would be, Is it hurting anything? I really don't like it.

And what is causing the issue?

My last motor(stock 98 LS1) in this truck didn't do that.

chevyss2008

I have a 2000 WS6 and had cam, timing etc installed...Also installed was a new high pressure oil pump...my oil psi sucked after that...The new oil pump cratered and I had another stock pump installed at another shop...at start, im 40psi....oil psi will drop to 10-12 at red light and back to around 35 when driving, and that's with 20w-50....Before the cam and stuff I was at 45 cold, and 35+ all other times with 10w-30..