If you are certain that the noise is from the top end, the cam bearings could be bad.
If I remember correctly, the 3.0 V6 has an overhead cam for each cylinder bank. The top end is made up of;
Camshaft, bearings, rocker arms, and springs which close the valves.
The top end takes a beating over the years every time you start it. This is because this is the last place oil gets to when the motor is started. After time the components wear out.
Since the noise is a constant grinding, it is most likely that it is the cams and /or cam bearings. If you change your own motor oil, clean the drain pan really good and after you pour out the oil look at the last bit of oil in the pan under a light. Check for tiny pieces of metal.
If you see silver metal, you are on the way to failure. If you see brassy colored metal. Be prepared for it to give at any time. A likely scenario is the metal will ruin the valve stem seals and you will start billowing smoke out of the exhaust pipe.
If you consider fixing the vehicle, don't just re-build the head, get a full re-build. The contaminated oil will or has damaged bottom end components as well.
I hope this information helps.
Monday, May 2nd, 2011 AT 11:51 PM