Wear on a balance and cam

The Isuzu 2.2L vehicle from 2004 arrived with a sound of propellants, the camshand of the rockers and the propellants were changed; When a week passes, the sound begins as a result we have a totally worn balance and its respective cam. What could cause this damage?; YEAH; The material is good the oil pump in with the vehicle in idle has 40 psi and 4000 rpm rises to 60 psi of pressure ...