timing on a 1986 320i

[solanog]

Hi, I own a 1986 e30 320i, I don't know how to adjust the timing or have not been able to adjust it accurately.
So which are the steps for adjusting it and what are the markings that I should look for?
This car has a marking in the front of the engine and has something like a Z on the front pulley and some other marking. Are this to show where should the timing be adjusted or what? Do I have to disconnect the vacum from the distributor? What are the RPMs for adjusting the timing?

Thanks for your help.