I have a 97 silverado with the 5.7 vortec in it. since i bought it i have put 20,000 miles on it, it now has 180,000 miles. and now i have motor knocking problems and i can hear the valves ticking when its cold. after it runs for about a minute it all goes away and runs fine until it is completely warmed up and the oil pressure drops to like ten pounds, still runs fine but when sitting at a stoplight with the brakes applied the oil pressure is way down and the check guages light comes on until i accelerate. i have been told the main bearings are shot, but i dont really know. maybe a bad oil pump? can i install a high volume oil pump?. or should i just rebuild?

 

My guess would be the oil pump is bad if your oil is filled up to the right level. I am sure someone here will answer the other Q's you have.

Welcome to CF!

 

i had the same exact problems just 3 days ago. i had a new oil pump installed and it all went away. it is deffinatly your oil pump. get a new one

 

Agreed

 

You should have someone perform a mechanical oil pressure test. Also it could simply be the pump or a clogged pick up screen. If you turn it off and then restart it does the oil pressure come up temporally? It it does that is a sign that there is sludge in the oil pan as it gets sucked up on to the screen oil pressure is reduced,when you turn it off all the sludge falls off and pressure comes back. However if damage has been done to the bearings all ready you will not get pressure back even with a new pump, if bearing clearance is to big the engine can not produce pressure

 

It is very typical for a 350 to have sporadic oil pressure levels, but if it is already knocking, depending on funds, and how attached you are to the truck, a rebuild would not be a bad idea, but if you hate the truck, throw a new oil pump in it, fill it up with some thick oil and treatment and sell it to someone you don't know, sounds crappy, but again, if it is already knocking and ticking, the damage has already been done

 

I would try the new oil pump and have the oil pickup screen cleaned.

Then run shell rotella 15w40 oil, with 1 qt of lucas oil stablizer and a wix oil filter.

If that does not do the trick and keep the oil girl running for awhile then I guess a rebuild is in order.

I ran valvoline 50 weight racing oil in an old jeep once, with worn out motor, kept oil pressure up to around 40 psi at 50 mph. Ran it that way for 3 years, then got a new long block.

If you can not get the oil pressure up: selling it as a truck with good motor to some poor working stiff is just not my way.