SBC Block Casting Numbers

The block casting number on smallblock and big block Chevy V-8 motors is located on a ledge found at the rear of the block, most often on the driver's side. This ledge is below the deck of the block and the ledge forms the mating surface between the block and the transmission bellhousing. Some of the later model blocks have the casting number on the passenger side of this ledge.

The number itself can have 6, 7 or 8 numeral digits. They might look like this “361959” or “3970010” or “14015445”. The block casting numbers do not have any letters in them. There are sometimes other individual letters found on blocks like “GM” or “CFD” for the Central Foundry Division, but they are not part of the block casting number. Also some of the later blocks have the size of the motor shown in liters. You may see a “5.0” (305) or “5.7” (350) cast on the rear ledge of a smallblock or a “7.4” on the side of a big block 454.

On the side of some later blocks the last three digits of the block casting number are cast into the block, but these are difficult to see when the engine is in a vehicle.