All early Chevrolet Corvette factory exhaust manifolds are cast iron. Since the manifolds are cast, the actual casting number and date are raised above the actual surface of the part. Most casting numbers are visible when the manifold is installed on the engine. The casting number location and casting date location will vary from year to year and sometimes manifold to manifold. Some manifolds will not carry a casting date at all. Small block manifolds do not carry a year designation. 2" outlet small block manifolds will have a casting date, while most 2 1/2" outlet manifolds do not have a casting date. There were two types of manifolds being cast for Corvette, the first from the Flint, Michigan built engines, which were cast in Saginaw, Michigan. All small block Corvettes used these manifolds. The second type was cast at the Tonawanda Engine plant and all Corvette big block engines used these manifolds. The big block manifolds will be discussed and identified in the second installment of this article.