But this isn't a Cossie is it? I think the guy has a 2.0 DOHC 8v I4.

Are you getting a clattering from multiple valves at the same time or a persistant tapping from one tappet? If its a clattering they have always been a bit prone to this, particularly on starting. My Dad had one and it did it from new for the first 5-10 seconds when it had been left for a a day or two.

Have you fitted a proper Motorcraft oil filter? It always seemed a lot worse with a pattern filter in it. Probably because the non return valve in it was not up to the standard of the Ford one...