MBIA is selling its 1838 Investment Advisors equity asset management unit to 1838's management and Orca Bay Partners, a private equity firm. Terms were not disclosed; the transaction is expected to close on or about May 10, according to a release from Orca Bay Partners. MBIA executives are selling 1838 to concentrate on the fixed-income asset management business, said Michael Ballinger, MBIA corporate communications director. 1838, which was acquired by MBIA in 1998, had $3.6 billion under management as of Dec. 31. Officials from Orca Bay did not return calls seeking comment by press time.