[faapgar]

Neil said it is obvious if you look.In 1977 Porsche changed the oil delivery to the main bearings.When you look at the left bearing it shows a shiny aluminum disc around the feed hole.They did this 1st on Carrera 3.0 & 3.0 Turbo.If you look at the saddle boss it looks like you stuck your pinky into a cake and left a depression.The oil delivery hole is also increased in size.Oil delivery hole sits about 4-5mm below the bearing.I will try and get a case off the shelf tommorow.I have a 77 turbo case.On bearings that are older and have a dark stain around the delivery hole in the back of the bearing the need for the chamfer is obvious.Maybe Neil will expound on the change to the main bearing saddle for the change of delivery.Fred