Well I have checked the engine running without the belt, and the sound is still there, laud and clear.
as I stand next to the front whell "either side" the sound is so clearly comming from between cylinder 3 and 4 just right under the valve cover.
Its very clearly when you move your head from side to side just above the valve cover.

and it almost sound like the whole stuff inside is ratling around, like something is realy about to snap or have a huge tolerence play to make this sound.
Not so cool