I take the cams to a machine shop and have them groove it in thier lathe, .030 deeep and the same width as the oil hole . As far as the oil return, if you have bushed rockers(non roller on the shafts) you probally won't have a oil return problem, if there true roller rockers you may have to add a .080 oil restrictor in the oil passages to the rockers I have several wedge motors with Indy heads and thier external oiling with one set of Harland Sharp single shaft roller rockers and the other one has a set of T&D stock type single shaft roller rockers, you absolutely need to restrict the oil flow on them The new World blocks, both wedge and Hemis, have .040 oil restrictors in them from the factory, they oil the rockers full time I have a .039 restrictor in my street 518 C.I. 440-1 Indy heads wedge motor using the Harland Sharp a stock 6 quart 1970-71 street Hemi and .080 restrictor in my 527 C.I. Indy head bracket race motor with a 10 quart Charlies race pan with a kick out Both oil the rockers profusedily(SP) EDIT. I will problally change the street motor restrictors to .035 and the race motor to .039 from the street motor