Just for interests sake, here are some pictures of
the Variable Valve Timing setup that the 4.2 uses.
In the first picture you get a top down look at the
two cams, you can see the VVT hydraulic mechanism
sitting on the front of the exhaust cam sprocket. If you
look closely, you can also see the brass/copper colored
VVT activating valve at the left side of the head, and the
extended/enlarged camshaft bearing cap on the exhaust
Here, you can see the front cap (lying off to the side) and
the spool valve that activates the VVT on the exhaust
camshaft. Transmission guys will recognize how this
operates. The camshaft is hollow and engine oil pressure
is fed to the retard/advance unit that sits on the exhaust
cam sprocket and that's how they control it.