Saginaw Metal Casting Operations is an automobile engine foundry plant in Saginaw, Michigan. Opened under GM management in 1919, the factory produces engine blocks and cylinder heads for General Motors vehicles. The factory currently occupies 1.9 million square feet on 490 acres. Historically in September 1927 it was known as the Chevrolet Grey Iron Foundry. In the past when it was called GM-Saginaw Product Company (SPC) a cloverleaf casting symbol mark was cast onto the iron component.