How to Identify Chevy Engine Block Numbers

by Floyd Drake III
itstillruns article image
chrome engine image by Thomas Czeizinger from

If you're searching for a Chevy replacement engine or looking for an engine to hot-rod, locating one is as simple as identifying the ID casting numbers found on the block. Chevrolet has an efficient numbering system for all of its parts, and a shortened version is stamped directly on the engine. A Chevrolet engine ID number listing must be referenced for identification. The code contains a prefix of five digits identifying date and location of manufacture and a suffix comprising two or three letters that give all the necessary engine information, including size, model year and horsepower.

Step 1

Locate the engine ID number located on the engine block. The location of this number will vary depending on the engine size. According to Nasty Z28 Second Generation Camaro Owners Group, the number for a small-block V8 is located on a pad at the front of the block on the passenger side, near the cylinder head; the number may be obscured by the alternator. For big-block V8s, the number is on the block above the timing chain cover. Six-cylinder numbers are on the passenger side of the block near the distributor.

Step 2

Decode the engine ID number prefix. The number is seven to eight characters long and includes both numbers and letters. An example is T0830CTY. The first five digits, or prefix, identifies the location and date of manufacture. In this case, the engine was produced in Tonawanda on August 30.

Step 3

Decode the engine ID number suffix. The suffix identifies the engine displacement, horsepower, year and vehicle model. In the example ID number T0830CTY, CTY decodes as a 1970 396 c.i.d. Camaro with 375 horsepower. The suffix must be compared with a Chevrolet engine ID number listing. Many online sites have substantial listings, but in case of an oddity or difficulty with an older engine, contact a Chevrolet parts department for a definitive answer. At GM Parts Direct, you can enter the code in the search box, or send a request to customer service for suffix identification.

More Articles

article divider