If its the timing belt slap noise, its hiting the timing belt cover, thus the noise you hear. You have 2 options. One, remove it and let it run without the cover or, two, go to a Ford dealership and have them replace it with a larger one(this is what I did).

If the noise sounds like a sewing machine ticking, it is coming from the mechnical valves. But this is with older zetecs so that may not be the problem.

My ride(Cardomain link) : '95 Contour 16V Zetec DOHC, Teal , ATX Born on Sep. 4, 1995 86+ miles *LEDs mods are on their way!*