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Chevy Small Block Casting Numbers

8/26/2021
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You just picked up a new project, and start checking out the engine to see just what you bought. You know it’s a small block Chevy, but you want to know a bit more about it. Is it the original for the vehicle? Or has the transmission been changed? Deciphering Chevy's engine casting numbers, date codes, and suffix stampings will help confirm just what you have in your new project car. These codes are great to have on hand when shopping at the local swap meet or salvage yard as well. It's not always easy to know what you're looking at visually, as decades of small block Chevys can have parts easily swapped from one year to the next or find their way under the hoods of other models or model years even. Want to know exactly what you have? Let’s find out!

What's The Difference Between The Casting Number And Engine ID Code?
A Typical Small Block Chevy Casting Number

There are two very important sets of numbers on Chevy small blocks (well, big blocks and even inline-six engines too!) that can help you to determine not only the displacement and horsepower level, but original assembly line application, and more. These two numbers are the casting number and engine ID code. As the name infers, the casting number is cast into the block when the block itself is cast. This casting number will denote engine displacement, 2 or 4 bolt main caps, application year or year range, and often any specific application notes. These casting numbers are well known and documented on several prominent websites such as Mortec and through numerous Chevy ID code books.

The Chevy Engine ID Code Features A Prefix And Suffix Code That Provides Key Engine Specs

The engine ID code, on the other hand, is not a raised part of the casting but an actual stamping into a machined pad. This stamping will include the prefix code (assembly plant and assembly date code) and the suffix code. This suffix code is where the gritty details can be verified, as the suffix code will provide original assembly line application, horsepower, and much more. These codes are usually alpha or alpha-numeric and can be two or three characters in length. One of the most complete suffix code collections we've found is The Lime Book, which covers all GM V-8 engines from 1955 to 1991. Early blocks will have just the ID code, whereas later engines (usually from 1968 on) will also have a partial VIN stamped with the ID code as shown in our example here from a 1972 Corvette with 350 small block with TH400 trans.

Where Are Chevy Small Block Casting Numbers Located?

On a small block Chevrolet, the casting number is found at the rear of the block on the driver's side (as is with Chevy's big block engines). The engine ID code stamping is located on a flat pad in front of the passenger side cylinder head (big blocks can be in the same location or above the timing chain cover, with inline-sixes stamped on the passenger side of the block behind the distributor). Sometimes the engine ID code is obscured by the alternator. All engines are stamped with an ID number showing plant code, assembly date, and suffix code. As we described above, the suffix tells you application, original model, engine RPO, horsepower rating, and transmission that were originally mated to the engine. Below we'll break down the ID codes prefix and suffix sections.

This Block Carries A GM Goodwrench 350 Crate Engine Casting Number

Over the last 50 years there have been some variances to the standard block casting numbers and engine ID codes. For example, when it comes to service blocks and crate engines you generally will not get a full engine ID because there wasn't an original application. You will usually find a "CE" for Chevy Engine. Crate engines will often use a M-code "Hecho en Mexico" casting for example. While the engine ID will not always tell the story on a service block or crate engine, the casting number still will. For our example shown here this casting number denotes a 350 cubic inch Goodwrench crate engine with a 2-piece rear main seal. Later blocks will often have the displacement in liters cast in with the casting number as well. It is common on these later blocks to see "5.0L" or "5.7L"

How Do You Decipher SBC Engine ID Code Stamping Numbers?

Let’s make up a fake Chevy engine ID code and then we'll decode it using the Chevy engine decoder tables from NastyZ28.com. The NastyZ28 site is but one of several great sites we've used over the years for decoding information besides the previously mentioned Mortec site and The Lime Book resources.

Engine ID Code: V0801CML (This ID is completely made up)
Chevy Engine Plant Code Listing

The first letter of the stamp tells us where the engine was assembled. In this case “V” stands for Flint, Michigan. The numbers that follow are the actual assembly date. These four digits are the numeric code for the day and month. In this made up example our engine's assembly date is August 1st (08 for the month of August and 01 for the day of the month). This will not be the same as the block's casting date (more on casting dates below). The “CML” that follows is the suffix code.

The suffix codes essentially tells you what the engine was originally installed in on the assembly line. Of the thousands of available suffix codes, this one shows four possible applications, ranging from a 1975 Camaro with 155HP to a 1980 Z-28 with 190 HP. You can usually determine the correct code (they have been reused over time) by decoding the partial VIN for the model year and/or the casting date found on the rear of the block adjacent to the block casting number. Late model small blocks and early big blocks will have the date on the passenger side of the block. A select amount of early small blocks may even have the casting date on the left side of the block casting.

  • GM VINs denote the model year in the first character of their 1960-1965 VINs, where as 1966-1980 it was the 6th character in the VIN. This will be denoted by a single digit for the last year of a decade (1966=6, and so on).
An Early Chevy Small Block Casting Date Code

Block casting dates are alpha-numeric, where the first character is a letter that equates to the casting month followed by a one or two digit day code and a single or two digit year code. If the year code is a single digit you'll have to use other block identification codes to confirm decade.

  • A=January
  • B=February
  • C=March
  • D=April
  • E=May
  • F=June
  • G=July
  • H=August
  • I=September
  • J=October
  • K=November
  • L=December

Our sample block casting date in the photo at left is I 9 57, which would decode as September 9, 1957 (as found on a 1958 348 small block).

The folks over at NastyZ28.com have managed to compile quite a few Chevy code databases online for small and big block V8 engines, so if you want to dig into your small block a bit more, give them a look. Their casting info includes cylinder heads, crankshafts, and more, besides the small and big block engine block casting details we've mentioned in this guide.

Chevy Engine Casting Numbers Decoding Help

Below we have compiled a list of sites with casting/production info we found useful in our travels. Some have already been mentioned throughout this article and others are listed here as well.

Updated by Mark Houlahan

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