Man! that poor engine has so much sludge it looks like it had an internal fire. Is it just my eyes or does the gear on the front of the cam look like it's got a couple of broken teeth? Wouter, that is a nice looking car, I'm sure you will have as nice an engine when you are done. Good luck.
Looks like an original GM timing gear. Back then the gears were encased in a plastic [nylon?] to reduce noise. Unfortunately they didn't have the longevity of an all steel gear set. Often the plastic breaks off and ends up in the oil pan & oil pump pick-up.
