valvetrain noise 5.9 magnum

Magnums with factory heads use a shared pedestal. They shouldn't ever "loosen up". But - things wear. The cam might not have, but I can tell you the lifters wear internally (the plungers and the bore they ride in), the lifter bores wear, pushrods and the contact points wear, and the valve stem wears. Over time the wear can "remove" the preload or cause enough oil pressure bleeding that the preload isn't enough. RPMs are not the only thing that kills engines faster. Full throttle does, intermittent detonation, cold starts, cheap filters... All can add to it. If you've ever heard a high-mileage Magnum you usually hear a little lifter noise. It's not a big deal. When/if it starts to smoke or you get a lot of visible blow by with it running and the oil fill cap off then things are wearing. My thought was if you were thinknig of changing something - don't waste time diagnosing and repairing - make the decision and then get things set up properly. Lifters are not part of the heads and they can be changed by removing the intake and rockers - just make sure the oil holes are pointing towards the valley.