2000 Opel Zafira Noise in the engine

Noises problem
2000 Opel Zafira 4 cyl Front Wheel Drive Manual 190.00 miles

I here a noise infront of the engine(Number 1 Cylinder), I have already changed the 16 Tappets and check for the Cam Lobes but still. The noise seems to be somewhere in the Timing belt and it´s Camshaft gear section. What is this noise?

Thanks