Milling the gears to make them lighter, probably for racecars only, purely to save weight.

Cam timing is done with offset keys. 2 valve engines of every brand with limited breathing typically require 4° of timing generally gives the best average torque. The factory spec is 0, but they don't actually set it, the parts just get tossed together and you get something around 0. The worst timing I have seen from buying a cam and tossing it in is 10° retarded. Degreeing in a cam is an essential part of engine building, i consider it as important as ignition timing.
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69 142S Overdrive + 69 164S Manual