White Engines was acquired by an investors group.

Senior executives of the Canton, Ohio-based automotive diesel manufacturer, the oldest such firm in the United States, were among the investors. The new majority owner, Donald C. Stewart, said the purchase price was $56.5 million. Stewart, a private investment banker from New York, has moved to Ohio to take over as president and chief executive. Investor John J. Lennon, the current chairman and chief executive, will remain chairman. Joseph G. Scheetz, another investor and currently the firm’s president, will become vice chairman.