What is a broach mark and where Is it located? I have a 1957 Corvette. Thank you for your help.


The broach marks are on the surface upon which the engine numbers are stamped. They are

very fine parallel lines In the direction of front front to rear on the engine that make up the surface finish of the pad. The broach marks were put there during the engine machining process by the broach machine, which was preparing the flat top surfaces, or decks of the engine in the machining operation. That machine was slicing off a thin layer of cast Iron material like slicing a thin slice of cheese.  The broach cutter blade left those fine parallel lines, which on an, old engine are sometimes almost invisible to the naked eye. Examination of the broach marks has become one of the ways to determine if the engine has been re-stamped, or if it is original. It is not fool proof, but it can be helpful to a person, who has studied those marks over time.