Pressure is at 4 bardepends on where its worn if camshaft surface then needs both rings and camshaft , so prob just best to replace the camshafts form the off rather than a redo if dont work if only try the rings as others have done to find most times its both, do need to do a oil pressure test on engine before anything else first as if low oil pressure its going to be other issues as well perhaps, ie if engine ever run low on oil could of caused damage to bearings and oil pump etc
Pressure is at 4 bar