4.7 V8 engine durability questions?

These are not bad engines but because Chrysler designed them to run higher cylinder head temps (for emissions purposes) they must have the oil changed faithfully or they will sludge up and eventually destroy the engine. It's best to run a synthetic like Mobil 1 in it and change it often. Also you never want to overheat one of these engines. It will most likely be garbage if you don't shut it off and fix it.

I wouldn't buy a used one without being able to pull a valve cover off to see if there is sludge in it.