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The head shop is used to cut the proper angles into the seat area, regardless if it's an insert or an integral design. A professional shop will use this style of machine to accurately cut the angles on the seat for proper airflow and valve sealing. A less expensive approach uses stones to grind the valve seat angles. Although it is an accepted commercial procedure, this style of valve seat work has no place on a performance engine. Always port the cylinder head before cutting the final valve seat angles. A good shop will "rough in" the valve angles as a guide for their porting work, then do a final seat cut when the porting is done.