When the engine is cold the oil is thicker and the pressure is higher, thus keeping the weak HLC pumped up. As the engine warms, the oil thins and loses pressure and the HLC collapses enough to allow a tick.
The best diagnosis I know of is the Herr Fuchs finger check, which you will find if you do a search. The standard, though, is to replace the entire side since you probably have other HLC's ready to start ticking.
I am clueless as to the rich mix on one side. The only thing I can think of is that the idle air tube on that side is blocked allowing a rich mix.
On the timing, the CD says 12-19 with vacuum so your local source is correct.
BTW - There is a great source for MB knowledge and parts in Australia. Name is Davide Frada, and his email is firstname.lastname@example.org
. I bought a set of Euro cams from him late last year.
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe