What are some ways to tell a 1.9l solid grind camshaft from a hydraulic camshaft? I read something about a crescent oil path, but I am not sure I understand. It is brand new old stock, with a "73" stamped with white paint. I don't know if that is the year, or not. It has "GM," and some other numbers stamped into the side of it, but it isn't in front of me now. The tube is deteriorated and all I can really make out is "Nockenwellen," and a part number. When I get home I can give more info.