Many people think that the displacement of an engine is the only way to tell whether a particular block is defined as ‘big’ or ‘small.’ Sadly, this is not only a false assumption, it can be patently incorrect even within a single lineup of engines from the same era. For example, in the 1960s and 1970s there were 400 cubic inch small block motors and 396 inch big block motors from the same vendor. So what does it take to qualify as a big block engine?
Essentially a big block engine is just what its name states: an engine bored from a big block of metal. A small block is bored and refined out of a small block of metal, and different manufacturers have defined those block sizes differently for their own purposes. Further complicating the matter is the fact that manufacturers have refined their definitions over time. Still, the basic core of a big block is the fact that the manufacturer has crafted the engine out of a much larger solid block of metal.
Larger metal blocks allow for larger bores, or the circumference of any cylinder. Since the size of a cylinder is only defined by its circumference and it overall height, referred to as stroke, it is safe to say that big block engines can have larger cylinders. Larger cylinders tend to be capable of generating more power, and that means that more metal is needed between each cylinder. This means that smaller blocks have less overhead in terms of bore than they do cylinder without having dangerously thin cylinder walls that might crack under pressure.
Big block engines are thus capable of larger overall displacements and performance with less risk of failure at the expense of overall weight and size. Big block engines cannot fit into smaller vehicles, though the exterior difference in size is usually only a handful of inches on any given size. The difference in weight can be far more tangible, especially because it necessitates extensive adjustments throughout the structure of the vehicle as well as heavier-duty transmissions and other components to handle the additional power that big block engines can generate.
Not all big block engines are necessarily incredibly powerful; some are simply designed to be reliable and durable under constant usage patterns. These big block engines are usually found in full sized commercial vans, where power is not necessarily important as bullet-proof reliability while carrying a full payload and/or towing. These same reasons are also why big block engines can also be found in full sized trucks.
- What is a Small Block Engine?
- What is a V6 Engine?
- What is a 350 Engine?
- What is a Rebuilt Engine?
- What is a Two Stroke Engine?
