Delphi Automotive replaces Titanium Metals Corp. on the S&P 500 on Friday after the close. The change is triggered by Precision Castparts’ acquisition of Titanium Metals. Delphi, based in England and with US offices in Troy, Mich., makes vehicle components. The stock will trade under the symbol GICS. Stock of companies joining the S&P 500 often rises because many portfolio managers try to track the index. To do that, they must buy shares of companies added to the index.