I have a dodge dakota with the v8. I replaced the oil pressure sending unit and oil pump and cleaned the pickup screen and oil pan. When i start it up it gets great oil pressure but after it runs for a few minutes and i rev it up the oil pressure will drop to zero, then you can here the valve train tapping. if you turn it off for a minute and start it back up, you again, get good oil pressure but then it drops again. Any ideas?

 

Plugged oil galley(or two) or a bearing or two could be going.

Thats my best guess. Not really sure what else it could be. There isn't a whole lot to go wrong when it comes to the oil system, and if you replaced everything around the oil pump including the pump, then all i can think of is the engine itself. There's a lot of oil galleys in there, and if a main bearing is going that could cause oil to not build pressure.

I know you've said you've got a valve knock, but could there be a rod knock as well?

 

No rod knock or elese it would always be knocking if a main bearing was going. The valve train only tappits when the oil pressure drops. I might just take off the intake and try to clean the oil return passages and stuff. any other ideas anybody?