astra engine

so recently my engine (C14NZ) made a weird noise, it's not any form of engine knock, it kinda sounds like it's scrapping or boiling. the engine has oil. it sounds like its coming from the cam cover. The engine still runs like it always has ran. any ideas?

I need an small auto engine for a Astra estate need it to be in Scotland and must be less then 150pounds. mine has giving me a the ghost and now will not start and i have replaced nearly everything on the engine and it still won't start. Aslo looking for some bonnet lifters. looking for an...