Flint Truck Assembly is an automobile factory operated by General Motors in Flint, Michigan. It is the city's only main plant after the closure of Buick City. The Flint factory currently produces full-size GM pickup trucks. Engine block and cylinder heads were cast at Saginaw Metal Casting Operations, internal engine components were created at and the engines were then assembled at Tonawanda Engine and Romulus Engine. For most of the 20th century Flint Assembly was the main plant for all Chevrolet vehicles.