Join Date: Dec 2006
Location: Santa Clara, CA
Summary: If there is an issue with the valve lash adjusters (VALVE LASH ADJUSTERS, people -- NOT lifters) not pumping up that causes the engine to sound tappy, it's harmless to the engine. Back in the old VW Beetle days we had the saying "a tappy engine is a happy engine", of course that was with a vehicle that had solid lifters and rocker arms with screw adjusters rather than with a roller cam follower directly pushed on by a cam, but same principle applies -- it's too-tight valves that cause issues (i.e., burned valves), not too-loose valves (which cause a slight loss of power but the valves tend to live longer too).
If there is an issue with a valve that burns easily, you have a 5 year powertrain warranty, and I can guarantee you that it will burn within that 5 years, cause a code, and be warrantied.
I asked my (non-Chrysler) mechanic why there was that big foam and plastic atrocity on top of the engine and he replied, "it's for sound deadening, because this engine makes a surprising amount of intake and valve train noise and people would complain if that sound deadening wasn't there." All of the new aluminum engines sound noisy because they don't have the cast iron mass to absorb noise that the old iron engines had. My guess is that this also explains why the engine seems a bit noisier on one side than the other -- if you pop up the plastic monstrosity you'll notice that the tuned intake manifold runners join on the driver's side, and it is plastic, so it has *no* sound deadening properties and transmits valve train noise directly, this also means that the foam sound deadening material is thinner on that side.
My old 4.0L made plenty of clattering from its hydraulic lifters on cold start, and it had enough sound-deadening iron to use as a boat anchor. By comparison my Pentastar is quiet and smooth. I have 9,000 miles on it now, and notice the valve train is slightly more clattery since my last oil change at 8,000 miles, but I'm pretty sure that's the oil I used, a synthetic that's on the thin side of 10W30. I'll switch back to the previous oil I used at 12,000 miles, and I expect that'll be that.
One last thing: My understanding is that the Sport models don't have the sound deadening blanket under the hood that my Rubi has. My guess is that this does make a real difference in how loud the engine sounds from the cockpit and from outside the vehicle. If there's other cars around it's hard to tell that my Rubi is idling even if you're leaning against it, I've had more than one person leaning against my Rubi as we're watching the next person in line tackle an obstacle and suddenly start as he realizes that my Rubi is running, it's just in Park with the handbrake set.
Dog: Man's best friend. Cat: Man's weird reclusive roommate who poops in a box.