When it comes to threading these Rocker Arm Stud holes you cannot do it on a drill press. You cannot do it by hand. You cannot do it correctly in a Seat and Guide Machine. You see the Factory had their machining together when this happened. These holes are not just critical they are Super Critical. If they are just a bit to one side, just a bit crooked, just a bit not perfectly vertical then the valve train geometry will be blown. Valve Guides will wear out in short order, pushrods will bend, retainers will pop off and cylinder heads can be ruined.
