In essence, the difference between a big block engine and a small block engine is dependent on the engineers who designed them. Certainly, the big block engine is larger in size overall. The big block engine weighs more and the valve bores are larger, while the small block engine is built in Mexico as a crate engine for hot rod and restoration enthusiasts.
The Big Block Engine
Big block engines deliver increased power production with larger bores, valves, and ports than small block engines. They were originally designed for larger cars and trucks before being added routinely to most passenger vehicles. As it adds weight to a vehicle's front axle, it may sacrifice acceleration for power. For perspective, big block engines can hit 5500 RPMs.
The big block comes in both 2-bolt and 4-bolt mains. But don’t confuse “cubic inches” (as in displacement) with the physical size of the engine. The first version of the big block engine was introduced in 1958, the “U” Series, and was designed to power light-duty trucks and some of the newly designed passenger cars. The W-series, made of cast iron, was produced from 1958 to 1965, with three displacement options: 348 cubic inches (5.7 L); 409 cubic inches (6.702 L); and 427 cubic inches (6.9973 L).
The Small Block Engine
A small block engine is a miniature version of the big block engine with smaller bores, strokes, ports, and valves. They weigh less, which provides a boost to overall acceleration and handling. In terms of torque, they can generate up to 5800 RPM.
Prior to that, the small block V-8 engine was standard in most Chevy cars, varying over the years in displacement. The Chevy 350 cubic inch (5.7 L) small-block eventually became the GM corporate standard until its manufacture was discontinued in 2003. Currently the small block engine is built in Mexico as a crate engine for enthusiasts. The small block engine is commonly referred to as a “mouse motor.”
History of Production
Coined by Chevrolet to refer to large displacement V8 engines, 'big block' and 'small block' engines have powered its vehicles since the introduction of small block engines in 1950's Corvettes and Bel Airs. The small block V8 engine was well received for its agile combination of lighter weight and power, suited for hot rods and racing-inspired vehicles like the Corvette. Thanks to the small block V8, Corvette 0 to 60-mph launch times were significantly improved. As a result, other automakers such as Ford followed suit, manufacturing small block V8 engines for 60's models Fairlane, Windsor, and first-ever GT350.
In turn, big block engines were first introduced in 1958 as the Mark I or W series in response to increasing demand for passenger vehicles after World War II. These big block engines worked to power larger vehicles, including muscle cars.
Past and Current Uses
The decision between small block versus big-block engines ultimately comes down to power and torque versus acceleration and handling. Big block engines are constructed using iron (complete engine assembly of ~685 pounds), with Gen 5-7 big block engines capable of up to 700 horsepower. Small block engines weigh approximately 575 pounds and could handle about 550 horsepower with slight variance depending on the age of the block.
In terms of RPMs, big blocks usually have a cap of 5500 RPM, which is the limit due to its very heavy valvetrain. Small block engines come in a little higher (5800 RPM)
In short, big block engines deliver increased power at the expense of fuel economy, stiffer front springs, large wheels/tires, and engine bay space. They also require bigger brakes and allows for less room for cooling systems and accessory drives. Small block engines sacrifice power for being lighter weight and are generally less expensive to build with better fuel economy.
All in all, small block and big block engines form an integral part of your GM, Chevrolet, or Ford vehicle. With more than 100 million engines sold, it speaks to the longevity and history of this iconic piece of machinery powering our vehicles for generations.