Casting Date

Fig. 3.10.5

  The Casting Date number is located under the valve cover between the valve cover hold down bolts as shown in WHITE numbers in Fig. 3.10.5 . There are usually 3 or 4 digits, the first being a letter of the alphabet from A to L and sometimes M or in the case of a set of heads I have "S" and "T" representing the month of production from January to December. Usually "I" is not used because it can be mistaken as a "1". The next one or two digits is the day of the month. And the last digit some times two digits is the year of production. Usually there is only the last number of the year. You sometimes will find the last two digits of the year which makes it easier. For more info on decoding the casting date you may want to view the next few pages which will help you see which changes were made in which years.

For example the Date Casting number in Fig.3.10.5 is:

 A 257 so the "A" is for the month which would be "January" that is the easy part, then comes the day of the month. In this date code it could be the "2nd" day of January 1957 or the "25th" day of 1957/67/77/87. Now is where my "GUIDE TO CYLINDER HEAD CASTING DATES" would come in handy. Since this head has the valve cover bolt holes straight across from each other it is not a 1957 casting and since it does not have the center bolt valve covers it is not a 1987 casting. Next thing to check is does it have the accessary holes in the ends of the head. If no holes its a 1967 and if it does have the accessary holes its a 1977.

A = January

25 = 25 Day of January

7 = 1967 or 1977

 NOTE: I have a set of cylinder heads with the casting number "3998 991" and the casting date on the two heads are " S 28 2 " and " T 7 2 " . Since these heads were only made from 1967 through 1977 and the two heads came off the same engine I can only assume they were cast on the 28th day and 7th in 1972 . So where did GM come up with "S" and "T" for a casting date.

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