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Chevy Small Block V8 Engine Identification

What's The Difference Between The Casting Number And Engine ID Code?

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. 

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. 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.

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.

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"

General Decoding Information
This topic can be somewhat confusing, especially with the amount of information available and the interpretation of it. The primary pieces of information you'll decode are the;

1. Engine Code and
2. Partial VIN.
3. Casting Date.
4. Casting Number.

The engine code and partial vin # will accurately nail down whatever the thing is rather quickly, and the other information will fall into line with that.

"Numbers Matching"
This is my opinion, and the generally accepted norm:
When people say "It's numbers matching" - what they mean is the engine (or other component, i.e the transmission) can be MATCHED to the vehicle it was originally used in. This match is done via the PARTIAL VIN stamp on the component. The partial VIN will match the vehicles VIN. If it does - it's "numbers matching", otherwise - it's not. done. end of story. 
Some folks use these terms loosely, or will say "numbers correct" or something to that effect. But numbers correct is not numbers matching. Again, it either matches or it doesn't. If it doesn't match - is it correct? 
Numbers matching is important when you're trying to decode a Z28 or Super Sport where the VIN won't identify the vehicle as such. You need to decode the engine and see if it matches the vehicle, and if the code signifies Z28 or SS equipment. 
Lastly, in extreme cases, you'll want to verify the numbers stamped onto the component were the ones stamped into it originally and aren't restamped. 
The point of this page is to help you figure out how to decode stuff.

1. ENGINE CODE STAMPING NUMBER

All engines are stamped with an engine ID code, consisting of assembly plant code, production date and suffix code. V8 codes are stamped on a pad just forward of the right side (passenger) cylinder head.

The engine date must precede the car build date, otherwise something is amiss. Some engine machining operations (decking) will obliterate the engine ID.

Engine ID Code Example: V0101CLJ - (V = Plant, 01 = Month, 01 = Day, CLJ = Engine Suffix Code)
Another example: T0830CTY - (T = Tonawanda, 08 = August, 30 = 30th day, CTY = 1970 396 Camaro, 375 hp, 11.0:1, TH400)

Engine Plant Code

Engine Suffix Code

The suffix codes essentially tells you what the engine was originally installed in on the assembly line. 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.

Suffix codes are either alphabetical or alphanumeric. Select the portion of the alphabet for your code. For example, select "DTR-HQ" if you'd like to find code DZ. In some cases suffix codes are reused twice or more over time, in this event check the partial VIN code or block casting date code and then see what year the block was made to pin down what application your block was originally used in. This list of codes is a summarization, it is not complete nor all inclusive.

Small Block Engine Suffix Code Menu 
3N - CDR | CE - CMJ | CMK - CUD | CUF - DTM |DTR - HQ | HR - TBS | TBT - TJS | TJT - TXB | TXC - UTT | UTU - ZY

Big Block Engine Suffix Code Menu 
0FC - 9XZ | AAA - CTB | CTH - IJ | IK - MZ | Q - YZ

Note: CODE CExxxx (counter or crate engine) was used from 1968 to current year. It represents any CID and is used to indicate this particular engine was replaced under Warranty. It is a direct replacement for the original equipment. It doesn't indicate what the original equipment was.

VF292800 - is an example of a over the counter crate engine. "2800" is the last 4 digits of the GM part # for the crate engine assembly. The final digit could be a year code.
Another example: A Targetmaster engine (p/n 14009800) built in 1985 could have a code stamped as follows:
A0198005 (A = january, 01, 9800 = pn, 5 = 1985).

2. VIN CODE

VIN Code Format
The vin code format is stamped onto most engines. The format consists of divisional identification number, model year, assembly plant designation and vehicle serial or sequence number. 
In 68-69 model cars, the serial (VIN) number of the car the engine was installed in is stamped next to, or under the engine code ID. 
Starting in 1970, the serial number is stamped either above the oil filter, somewhere on the block pad (in front of the cylinder head), or on the transmission flange somewhere. Chevrolet issued technical service bulletins to indicate which engines were to recieve a vin stamp, so who knows what could have happend (or not happened).

VIN code format Example: 13N100001 
(1 = Chevrolet, 3 = 1973, N = Norwood, 100001 = Production sequence of vehicle VIN)

Assembly Plants

In 1972, plant codes changed to reflect the VIN code. For example, "NOR" = Norwood before 1972. In 1972 and on, it was simply "N".

3. CASTING DATE

Casting Clock 
On some Saginaw blocks, intakes and exhausts a "clock" was cast into the block. The clock is a circle of 10 dots, one dot for each hour of a shift (usually 10 hour shifts). An arrow points to the beginning of the shift an another dot outside the circle indicates what time of day the cast part was made. Anyways, that's what that circle thing is (if you happen to see it on something).

Casting Date 
Small block casting date is located on driver side rear of block on flange forward of bellhousing. Big block on the right side of engine above the oil pan rails.

Casting Date Example: E038 - (E = Month, 03 = Day, 8 = Last digit of model year (1978)).

Month: A = Jan, B = Feb, C = Mar, D = Apr, E = May, F = Jun, G = July, H = Aug, I = Sep, J = Oct, K = Nov, L = Dec

4. ENGINE BLOCK CASTING NUMBER

Notes (for below): "High Power" is the maximum rate HP this block was used for, "Low Power" is the lowest rated horsepower RPO engine the block was used in. "Main Caps" is the number of bolts holding the cap. A "two-bolt" main, or a four-bolt main. Four bolt main blocks are desirable in high performance applications because the extra strength of the additional bolts keeps the bottom end rigid and less prone to failure. However, a properly prepared 2 bolt main engine will work just fine (often times you'll lose a rod bolt before you break a crank because it's "only" a 2 bolt main).

General Engine Block Specifications

Other helpful sites

• NastyZ28.com (casting code info)
• The Lime Book (engine ID suffix code info)
• Mortec (casting info, date codes, suffix codes)
• SS396.com (VIN decoding/info)
• GM Parts VIN Lookup (VIN decoding and info for 1960-2020 GM models)

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