Ford 351C Screw-In Rocker Stud Conversion Blueprint - Boss Machining Specs

This document is a machining blueprint (cross-section drawing) of a cylinder head rocker arm stud boss, showing the specifications for converting a pressed-in rocker stud boss to accept a screw-in rocker stud. The drawing shows a sectioned cylinder head with the stud boss at top, with callouts giving the required machining operations: mill the boss down 0.300 inch parallel to the original surface; drill the stud hole to 0.376"–0.372" diameter to a depth of 0.88 inch; tap the hole with a 7/16"-14 UNC 2-B thread to a depth of 0.68 inch; and chamfer the hole opening to 0.469" diameter at 60 degrees. A reader (machinist or engine builder) can learn from this the exact dimensions needed to machine the head boss for screw-in rocker studs. The document contains no year, make, model, or part numbers; it was uploaded to a 1972 Ford Ranchero gallery alongside other Ford 351 Cleveland-related reference scans, but the drawing itself does not state applicability. The image is a clean line drawing with fully legible text.