Ford Repair: ticking from engine, ford f 150, catalatic converter

Question
I have a ticking comming from the drivers head or the exhaust. To the bare ear the noise is louder around the exhaust under the vehicle near the catalatic converter.  I have used a stethescope and the noise through it is louder on the exhaust pipe and the head.  Sounds like a lifter tapping but when I put the stethescope on the valve cover the noise is muffled.  Frequence changes with engine speed and sometimes will stop completely for a few seconds.  2000 Ford F-150 supercab 4.6 L V-8, Auto, air, RWD

Answer
Hilliard-

  My guess would be that the gasket for the exhaust manifold may be done for.  When those gaskets go out the header can sort of tap against the head and it sounds quite a bit like an engine tick.  Try taking a close look at your manifold on that side to see if there's any play in it.  Hope this helps.

Steve