Now that you know
what the codes are, where they can be found, and why they're
important, you probably want to know how to read them. Fair
enough.
Casting Numbers - Casting numbers usually
consist of seven digits. In some instances certain components are
referred to by the last few digits of their casting number.
Desirable cylinder heads and blocks are an example. You may have
heard references to a set of "461" small-block cylinder heads or an
"010" block. These are the last three digits of the complete
Chevrolet casting number (3782461 for the heads and 3970010 for the
block).
In some instances Chevrolet would alter casting
numbers by hand after the part was cast. This was done to make use
of existing stock after a major design change has taken place. The
normal practice was to grind off a certain amount of numbers and
hand stamp the new digits. These instances are fairly well
documented however.
Due to the enormous amount of individual
casting numbers produced throughout the muscle car era, we do not
have room to publish them all here.
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Date Codes - These codes are fairly simple to decipher. With
a few exceptions, date codes are alphanumeric sequences that will
tell you the month, day and year a particular component was cast.
The codes are presented in the following format:
The first letter
designates the month the piece was cast. Months run alphabetically,
starting with A (January) and ending with L (December). The F in the
above example represents June.
The second and third digits
are the day of the month the component was cast. These are listed 1
(sometimes 01) through 31. The 10 in the above example is the 10th
day of the month.
The final digit is the last number of the
year the piece was cast. Obviously all numbers 0 through 9 are
valid. In the case of the above example, the 5 represents 1965. How
do we know it doesn't mean 1955, or 1975? Because this code was
taken from a #3782461 cylinder head casting which was produced
between 1961 and 1966. (See what we mean by looking at all the
pieces of the puzzle?)
Occasionally, some date codes are
listed entirely numerically. In this system a code may appear as 1
12 5 with the first 1 denoting January. This is very rare however,
and chances are you won't run across many in this format.
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