Small-block Chevy cast numbers are engine serial numbers cast into the engine block, cylinder heads, intake and exhaust manifolds. They are used to identify the series of engine castings designed for a specific car model. You can use Chevy’s small block casting numbers to ensure parts accuracy in restoring your classic car, or if you are looking for a car, to make sure you get what you are paying for.

I would use an engine foundry number decoder book in some scenarios. Imagine this …

• You’re looking at a Chevelle 66 that someone has for sale and you want to know if they have the correct engine.
• Or … you’re in a trade meeting and a guy has some engine parts he’s selling. There is a set of camel hump heads that he claims are from a 327 that “came out of a Corvette.”
• You’re spending the day at a “U-Pick” junkyard. You are looking for an engine core for your classic car restoration project and you come across an Impala SS 65 with an engine on it.

To be sure, you would need to look up the casting numbers.

The Chevy small-block engine casting number can be found in the block hood housing section, just behind the passenger-side cylinder head. This number will indicate some notable design specs such as 2- or 4-bolt main bearing caps, which car models it was installed on, the years it was installed on those cars, and in some cases the horsepower rating. A few cast numbers were used for several different models, so when in doubt you will need to look up the suffix code stamped on the engine.

Chevy’s small-block release date would help you determine in which decade the block was released if the use of the release number spanned decades, such as the late 1960s through early 1970s.

The suffix codes were numbers stamped on the engine block at the time of assembly. They can tell you which car the engine was originally installed in, the year, and even the series of options for the car.

Generally when shopping for foundry number decoders, you will find foundry numbers and suffix codes in separate books. Cast number information for intake and exhaust manifolds, or cylinder heads is generally included in engine block cast number decoder books. Be sure to look up years of coverage when selecting a decoder. Some cast number decoders only cover the classic years from the 1950s to the 1980s and may not provide information on late-model engines.

Some of the more useful decoders come in smaller sizes that will fit in a coat pocket or toolbox, which is useful for junkyard scavenger hunts or trade meetings. Others come in larger standard book sizes and will generally include more images and diagrams than the smaller text-only sizes.

In any case, small or large, you will find them indispensable and well worth the price. Most casting number guides range in price from $ 15 to $ 30.