I have seen a few posts on this forum questioning if the 4.7 is an interference motor. Yes it is! I had one of my techs set the valve timing wrong today while replacing a timing belt. Broke all the exhaust valves and cracked the guides. This was on a VVT motor plastic intake manifold. Only VVT motors have them. Still not sure about the older ones with out VVT, but as far as I know VVT only controls the intake cam.