Chevy Big Block Identification

All engines are coded with a prefix and a suffix that identify the motor. The first indication that a motor is a Big Block Chevy is if the codes are stamped above the timing chain cover. All Big Blocks are stamped there. Small Blocks are stamped on a pad in front of the passenger side cylinder head and are often covered by the alternator.

The first few letters and numbers identify the plant it was manufactured in, followed by the month and day for example: S0924--S stands for Saginaw, 0924 is the 24th of September.

The last few letters of the code are the suffix code. This is the engine identifying information; it explains the year and original application of the engine. For example: a code of QB is a 1962 Impala, CID:409, HP:409, four-speed transmission and 587 dual quad.

Chevy Big Block engines are a series of large displacement engines including: 348 ("W" series only) 366, 396, 402, 427, 454, 502 and, most recently, the 572. The first series was the "W" series, which was used from 1958 until 1965. In mid-1965, the Mark IV series was introduced into production and has remained since. The 348 and 409 are exclusive to the "W" series, but the 427 is a crossover used in both series.

To determine what the codes mean on the engine, contact the parts department of a Chevy dealer, a Chevy car enthusiasts club or search Chevy engine codes on the Internet, there are many sites that list the definitions of the codes (see Resources).