How to Identify a Chevy Exhaust Manifoldby Floyd Drake III
Chevrolet exhaust manifolds are easily identified by the casting number; however, the casting number is not a code, so it cannot be deciphered. Referencing the number to a known Chevrolet exhaust manifold casting number listing is the only way for positive identification. When referenced, the listing identifies manifold specifics, including the year, vehicle model, horsepower and any performance specs. Chevrolet does not place the exhaust manifold casting numbers in a set location, and they may be anywhere on the manifold. A date code is usually cast as well, though not all Chevrolet exhaust manifolds have date codes.
Open the hood to access the engine. The exhaust manifolds are bolted to the cylinder heads, near the spark plugs. Since all Chevrolet exhaust manifolds are cast iron, the casting numbers are raised, not stamped, and they are typically visible with the manifold installed. A wire brush may be necessary to clean the number so it can be read.
Write down the exhaust manifold casting number. The casting number is a seven-digit number, "3840715," for example.
Search for the date code. If visible, the date code is a letter followed by three numbers, "C259," for example. According to Chevelle Stuff, the letter represents the month, "A" for January, following in order to "L," for December. The middle two numbers are the day of the month, followed by the last digit of the decade year. The example, "C259," decodes as March 25, 1969.
Reference the casting number to a listing of Chevrolet exhaust manifold casting numbers. Reference listings are available, including those found on Chevelle Stuff, Nasty Z28 and Out In The Shop.com. When referenced to the listing found at Chevelle Stuff, the example "3840715" is identified as a manifold from a 1964 327 cubic inch engine with 300 horsepower.
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