Instead of writing everything all over again I am just going to link to the original post , which has links to the grandprixforum where the discussion continued.
I am at my wits End with this oil problem. I thank all who can offer advice and direction .
Thank you so much !

Louis

Trying to help someone out 3800SC - Pennock'* Fiero Forum

Does the oil filter use a filter mounting adapter.....the type with the dual hi pressure bypass pistons (one pressure relief piston for each cylinder bank?.......could one of them be stuck open?

The motor is out of a 96 bonneville. I swapped out the oil filter adapter with a GTP one and I did install the spring and valve piston correctly. Last spring I thought I may have left out that spring and valve so I removed the adapter to find inhad the spring and calve in correctly All Along and installed a new spring and valve just because I ordered a new one from GM.
It there'* only one spring and valve in the adapter right? That'* what the parts diagrams show.
I've never heard of dual valves In The adapter. Does the series 2 bonneville motor need an adapter with two valves? Can you link me to pictures or explanations of what it should be like?
If there are two valves and each feeds each lifter bank, this could surely Be the issue and would be a much easier fix than pulling the motor out of the car and separating it from the tranny. Thank you and please Send me all relevant information.
Louis

Here'* the whole story so you don't have to go from link to link.

Ok , sorry but I've been asking around so much . Here'* the rundown:
1996 bonneville 3800sc (series 2) - bought the engine with 100k miles on it and I replaced the lim gasket with the zzp aluminum gasket and also did water pump, replaced rear main seal and cover plate gasket, put a 99 Grand Prix oil filter adapter on with the spring and check valve correctly. Also replaced lifters which were primed (soaked over night in oil and pumped before install) And also installed new pushrods. When running the engine I get 60 psi at idle so the oil pump is ok but only the pushrods on the alternator side of the engine are getting oil squirting up and the pushrods on the ac compressor side of the engine are completely dry. I tried motor flush and then rislone and the second drive with rislone the horrible tapping sound silenced and then came right back on the next drive. Thinking I had a clogged oil passage I tried valve medic and marvel Mystery oil but the rattlly tapping is still loud and noisy (no oil to that ac comp side valve train) . So I did a 5-7 mile drive with 2quarts 40weight oil, 2 quarts ATF, and 1 quart acetone. The rattle is still as loud as ever meaning no oil to that side. First I was told I prob have the rear main seal cover plate gasket on backwards preventing oil to that lifter bay.but then I read and see by the gaskets appearance that if that happened it would only be the balance shaft that would be starved oil . Now I am getting info about a dual check valve oil filter adapter that was needed and that that could be starving the ac compr side Lifters oil. I'd rather not have to pull the engine out and take it off the tranny just to find out that the gasket for the rear main seal cover was ok to begin with. Is there such an oil filter adapter with dual check valves? Please help!!! (Oh and thanks for reading this whole thing)
Louis

Bump , somebody'* gotta have some info out there related to what'* going on.

??

I've looked in the GM service manual. Nothing is mentioned about one bank being starved. I've been on this forum since 2003 and have never heard of anything like this.

I could say, remove the intake plenum, your valve covers and pull the rear hydraulic lifter and see if its dry. If you had a borescope, you could look into that bore and look at the oil out put hole to see if its clogged.
I doubt you will see much of anything. So really, your only option is pull the engine back out, pull the cam oil galley plugs out and find the blockage. I know you don't want to hear that, but I know the feeling and its hard work. I've had to pull the V8 out of my *-10 twice.

When I replace the pushrods (thought they were bent and making the tapping sound) the alternator side lifters had stiffness when pushed in like they were full of oil but the Ac comp side lifters were springy like they weren't stuck but had no oil pressure in them. They probably lost thier prime from running and pumping oil up but then not getting oil.
Any idea about the rear cover plate gasket being installed backwards a d that that may starve one lifter bank oil?

No clue sir. I havent had a 3800 apart in years.

Thanks so much for your help. I got a new rear cover gasket and by lookin at it I can see that if t was installed backwards it could interrupt the oil flow to the ac side.

Can you take a picture of it?