First step in diagnosing engine tap sound:

My RAVE CD is buried somewhere on my desk. Can someone advise where to connect an oil pressure test gauge on a 2003 Discovery 4.6 engine?

Can someone also advise what are the acceptable minimum values for a cold and then a hot engine both at idle and 2000 rpms?

 

Under 10psi at idle is the cutoff. You attach your oil gauge where the oil sender is screwed in.

 

Look at the sticky at the top of this section and read Josh's write up on setting up a guage.
Once you get it done, do a cold start, check the pressure at idle and at 2000 RPM's, then at operating temp do it again at idle and 2000 RPM's then get back to us with the 4 sets of numbers.