So far all the comments are good -but- you really should check the FSM as some old Mercs use the ATDC timing point, it's important as the ones that do use manifold vacuum to the advance biscuit not ported vacuum like most American cars.....

This threw me for a loop with my 1975 350SLC graymarket but it worked out quite well in performance and cool running engine .

I never passed 15MPG's in it but it never pinged, knocked nor failed to easily spin the rear wheels on demand .

Late ignition timing helps make a dead smooth idle, as long as it begins to advance when you open the throttle it'll be right, *do* get an advance timing light so you can check the full advance, all in timing too .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better