General Motors (GM), Detroit, announced it will make a $163.2-million investment in three manufacturing plants, including $12.2 million in the Defiance, Ohio, metalcasting facility. The balance of the investment will be in the engine facility in Flint, Mich. ($138.3 million), and the component maker in Bay City, Mich. ($12.7 million). The spending is intended to support engine production for the Chevrolet…