I seem to answer a lot of questions about Chevy engine numbers, so I thought I'd share some of my "secrets" here in a tech post. Chevy was pretty good about putting a lot of information on their engines, and the numbering systems have stayed mostly the same for a long time. The mid 50s and earlier engines are stamped differently than the newer ones, but the casting date numbers work the same back into the early 1930s. Each engine will have 3 or 4 number sequences that when combined, will identify what the engine is from. We will start with the block casting number, which is from 6 to 9 digits long. On the straight 6 engines, it is on the back on the passenger side of the block, hidden or almost hidden by the starter motor, or along the middle bottom of the block, possibly hidden by an engine mount. On the V8 engines, it is on the top of the block, at the back, above the bellhousing area. Casting numbers for Chevy V8 engines can be found at: http://www.mortec.com/ Casting numbers for Chevy 1937-1962 (stovebolt) inline six blocks can be found at: http://clubs.hemmings.com/clubsites/chevytalk/GMhistory/cast.html and for those and newer straight 6s try: http://www.inliners.org/casting/numbers.html At the same area where you find the block casting number, you will also find the casting date code. The date codes are sometimes ambiguious, because they don't have the whole year, only the last digit (with a few exceptions). The casting date code is a letter followed by 2, 3 or 4 numbers. The letter is the month, A = Jan, B = Feb, C = March, etc up to L = December. The second or second and third number is the day of the month. The last number (sometimes last two) is the year. Some examples: C 1 2 or C 1 62 if it's march 1st, 1962 or B 16 2 (for Feb 16, 1962) The casting date is usually a day or two or three before the engine assembly date, but sometimes it's weeks or even a month or more earlier. The third set of numbers is the engine number stamped into the block. It will be on a machined pad at the base of the distributor on straight sixes, or on the deck surface just in front of the passenger side head on V8s. Some newer V8s have it on a little machined pad just above the timing cover. The stamped code on 30s-mid 50s engines includes some variation of the car model code, and a sequential engine number, but no date information. An example is: JAD123456 J = 1951 Mid 50s engine have a sequential engine number, engine plant, the last two ditits of the year, and the letter suffix code. An example is: 123456 F56B F = Flint engine plant 56 = 1956 B = truck 265 with hydramatic The stamped code on 1957 and newer engines tells you the engine assembly plant, the month and day of assembly, and the type of engine and what it was used in. The code looks like this: F0306AF The first letter tells you what plant the engine is from, either V or F (Flint, MI), it could be T (Tonawonda, NY). 0306 is march 6th, the assembly date. Notice that the year is not given here. Before about 1960, the date does not have the leading zero, so in this example you would see F306AF. AF is the suffix code. It can be one or two letters on 1969 and older engines, and three letters on 1970 and newer. The first letter of the 3 letter code on early to mid 70s engines will often be C for Chevrolet car engines, and T for chevrolet truck engines. There are literally hundreds of suffix codes, and I will not attempt to list them all here. I do have some books that list many of the codes from the 50s to the 70s, in addition to the ones pictured here, if you need help finding one please send me a PM. There are also some wierd codes for replacement engines and crate engines, sometimes they include an R at the end of the suffix, or the suffix is CE for "counter engine" (or whatever else it might mean?). Trivia: the LS-7 crate 454 that Chevy sold in the 70s and 80s has the suffix code XCH. The last number sequence is the partial VIN, which was used beginning sometime in the 1960s. This will usually be found stamped next to the engine code. It will have 9 characters, the first three are the interesting ones, the last 6 will match the last 6 digits of the VIN that the engine was originally installed in. If you are looking at a car that claims to be "number matching", what that means is that the 6 numbers on the block match the 6 numbers on the car's VIN plate. If they don't, then it's not a number matching car! (and even if it has the correct number, it's possible it was restamped). We HAMBers usually don't give a shit about matching numbers, but at least now you know. Here's how the partial VIN breaks down: 12K123456 first number is the carline, which is 1 for Chevrolet, 2 for Pontiac, C for Chevy truck, T for GMC truck. Second number or letter is the year, it will be the last digit of the year on 1960s and 70s cars, and a letter starting in 1980. A = 1980, B = 1981, C = 1982, etc. Third letter or number is the vehicle assembly plant, in this case K for Kansas City.