Identification of the small block Chevy (SBC) engine requires searching for numbers and codes, and referring to sources to help identify size, date of casting and assembly, and, among other things, the specific application. This is significant to be able to get correct replacement parts and to be able to determine its proper application in restoration vehicles. Some very rare combinations have been produced, and collector car values are dependent on having the correct matching numbers.
Since its introduction in 1955, it is widely estimated as many as 100 million small block Chevrolet engines have been manufactured. It remained virtually unchanged until the late 1990s, when more modern designs were engineered.
The seven-digit engine block casting number will be found at the driver's side rear of the cylinder block above the flange for the transmission bellhousing.
The block ID code will be stamped (not cast) into the deck of the passenger side front of the engine. This number will be on a machined pad directly in front of the right cylinder head, and will also detail the assembly date and information about the engine application. Part of the vehicle ID number might be included.
The date the block was cast on first-generation SBCs is found on a ledge at the passenger side rear of the engine. This differs from the date of assembly.
A two-piece rear main seal was used on the SBC until 1986 when it was changed to a one-piece seal. The crankshaft flange diameter was reduced as well at the time of the change in seal design.
Recent variations of the SBC have been designed for newer applications. Many of these engines have the metric displacement (4.8L, 5.3L, 6.0L) cast on the passenger side rear of the block. Some also have the size cast on the side of the block near the freeze plugs.
