I had the same problem on the right mirrior my 48 Chev. I couldn't get it adjusted properly and I did take it right apart and tried turning that phillips head screw and still couldn't get it right. what I ended up doing was bending the arm to make it go where it needed to. A word of advice put some lock tight on the screw that goes through the arm that holds the mirrior on. I was driving down the road and the mirrior fell off.
