Dan/87/944na

Just put in new filter, 20-w50 dino and I swapped out my oil pressure valve with a used one to see if I would get any pressure. at first start up no pressure at all. I shut down checked everything and then put the old valve in and no pressure again. came back an 20 minutes later started up and had some pressure than it dropped back down to zero and the lifters started to clang then it would go up agian then drop and I just shut it off and threw a wrench through the windshield <img src="graemlins/cussing.gif" border="0" alt="[grrrrrrr]" /> (j/k about that last part even though I wanted to at that point) My question is does this sound like a faulty pressure valve? I was thinking the oil pick up also but why would it have different pressure readings sitting still in the shop. could it be gunk in the engine? I switched to synthetic and back to dino (started having problems after I put in the synthetic) I am so clueless at this point. I'm near Milwaukee if anyone wants to do some magic on my car...thanks all...dan <img src="graemlins/c.gif" border="0" alt="[ouch]" />