replacing valve seat inserts

A valve seat insert may be badly worn or it may be refinished previously so that there is insufficient metal with either condition, the seat must be replace the old seat removed with a speacilal . An electric drill is then use to drill holes almost through the insert . Then an over size insert installed . It may be necessarly to chill the seat & heat the head before the seat is driven into place. After instalation the valve seat should be ground