STOCK, original equipment camshafts:
For the stock cams, at .0787″ valve lift (2 mm), the timings are as follows, keep in mind that two types of these cams installation available, the 3° advanced one & the not advanced one.
R50/5, R60/5, and R60/6 to 1975:
BMW issued a SI on that camshaft, saying that some published information was NOT correct. BMW said the correct figures are:
Intake Opens TDC; Intake Closes 40° ABDC; Exhaust Opens 40° BBDC; Ex Closes was illegible, but I am sure it said 40° BTDC. If you were to look up the sprocket and camshaft in the present parts fiche, it would be 11-31-1-250-253, sprocket.
284° camshaft, used UP TO 09/1975, 11-31-1-259-262.
UNfortunately, BMW is confusing itself. You will find that other manuals say Intake Opens 40°ATDC….all the numbers are 40°; that includes the intake opening at 40° ATDC.