I have an LS1 with 109,000 miles this is a Z28 SS convertible with a 6 speed stick. The problem is that some one did not do the proper care for this car and the oil developed sludge which is causing me issues. the car starts and runs fine but when it comes up to operating temp it loses oil pressure and starts to rattle. if I leave it setting it does not happen it will run for a hour without an issue but as soon as I start to drive it the engine picks up sludge and loses oil pressure. if you shut it off let it cool and start up again the oil pressure comes back and all is well till you drive it again. I cannot spend a ton of money on this but if something simple helps please let me know. Archie

 

The simplest and easiest fix I can think of if sludge is the problem is change the oil with synthetic and let the oil do the work for you. This way will probably take some time and miles of driving to clean out the sludge.

Does the valve train make noise when the pressure drops?

 

make sure your using a quality oil filter. agree change the oil. actually change it again after several hundred miles. see if you can work it lose.

 

Most likely the engine is not picking up sludge. I assume you changed the oil? The sludge would sit at the bottom of the pan and it is the first thing that drains out when you do an oil change. If a motor has sludge in the pan you will see high oil pressure cold and you will see above average oil pressure do to the thickness of the sludge even warm. Lift tapping is also common on slugged up engines. At the dealership we would see it all the time. Cars traded in all slugged up and when we change the oil the pressure drops much lower then when the car was traded in. These car end up going to the auction.

Old school trick to clean them out was to let them idle with kerosene in place of the oil. After they got warm, drain it and put real oil back in, run it another 30 minutes and change the oil on last time. I DO NOT recommend that for your LS1

The weakest point on the LS1 is the oil pump. It sound to me like your oil pump is letting you know that it is failing. The LS1 is insanely strong and is easily a 200,000 mile motor yet you can find a lot of cars that have replace motor right around 100k. I bet 90% of those low miles cars with replacement motor are because of a failed oil pump. Whatever you do, DO NOT DRIVE THIS CAR!!. The pump can completely fail at anytime and you have about 10 seconds to shut it down. There is a small chance this could be the sludge under the valve covers is so backed up that it will not let the oil drain back to the oil pan fast enough and the car runs out of oil but with the LS1's history of weak oil pump I would assume its that until proven it was not.

Oil pump replacement is not cheap but if you price replacement engines the oil pump starts to look cheap.