Land Rover Repair: Disco II passenger side intermittent valve tic., bolt torque, low oil pressure

Question
John, I am trying to diagnose a 04 Disco II 66k miles.    It came to me to repair a valve tic that passed this truck through several local shops.   Some how I end up with the issues that other give up on.   I started be installing new rocker arms and shafts.  All seemed to be good.  It came back a couple days later with th same issue that comes and goes.   It has valve ticking from the passenger side only.   I put a manual gauge on the truck and it will fall to 5 - 7 lbs at ldle.  Close to 50 lbs at 2000rpm.  It acks like a lifter or several lifters loosing pressure.  I believe I remember reading that the passenger side lubes the bottom end.  Could bearing wear be causing  the passenger side lifters to loose enough oil pressure to  pump down?  The fact that you can make a couple trips with no tic and the next it will tic like crazy is the real mystery.   

What should e oil pressure range be?
Do the passenger side oil passages feed the bottom end?
Are there higher volume and or pressure pumps / relief springs available?

Many thanks....
Richard Grimes

Answer
We have gone down that road at Robison Service to no avail.  I think the tooling was totally worn out by 2004 when these last engines were made.  The ones we have taken apart have had improperly drilled and tolerances front covers (low oil pressure) loose wrist pins (rapping) excess clearance on piston skirts (rapping) poorly fitted liners (engine failure) and cracks in the blocks from head bolt torque (engine failure)

I'd give 9 of 10 odds one of these issues is your problem and if I were you I'd cut my losses and advise the owner to drive it till it worsens and meanwhile save for a new engine if he wants to keep that vehicle.