The debate is older than most drivers, but it all comes down to subjective preference. High-winding power vs. Earth-moving torque, high-note scream or ground-pounding rumble; whether you prefer a big block or a small block engine is all up to you and the personality you'd like your car to have.
Chevrolet debuted its seminal small-block (a.k.a. "mouse motor") in 1955, offering it in two basic flavors: a 265 cubic inch (4.3L) making 162 horsepower, which would later rise to 240 horsepower by 1957, and a 283 making 220 horsepower, later rising to 315 in Corvette trim). Shortly after introducing the small block, GM recognized the need to produce a larger V-8 engine to power its upcoming line of trucks and full-size luxury cars. It was at this time they introduced the Generation I "W" big block, so called because of the shape of its valve covers.
The original Chevy small block currently holds the record, as of March 2010, as the longest-lived engine design ever produced, and went through several changes over its documented 43-year production run. Generation II small blocks, known as the LT series, as in LT-1 and LT-2), went into production in 1992, and differed mainly from the original small block primarily because of their reverse-flow cooling systems. GM used the LT engine across its entire truck line, and for five years existed along side the Generation III LS (which would replace it in 2002, and is still in production today in Generation IV form).
Generation I big block (a.k.a. "rat") motors went through several iterations in their five-year production run; the 348 alone was offered in no less than eight different configurations, ranging from 250 to 350 horsepower. Those legendary 409s and 427s were Gen I engines. Chevy introduced the Mark IV, Generation 2 engine in 1963; improved cylinder heads, engine blocks and valvetrain made this new engine far more powerful and efficient than the last. Gen II engines ranged from 265 horsepower (1969, 2-barrel carb 396) to 430 horsepower (the legendary ZL1 427)
Big block engines have two major drawbacks: they're heavy and expensive. Big block engines are about 30 percent heavier than small-blocks, which is quite a lot when you consider it's all over the front axle. Unless you're shooting for something over 500 horsepower without nitrous/turbo/supercharger, any big block will cost you more to buy and build for the same amount of power. Original big-block powered cars (even relatively small 396s) usually command a serious premium over small-block cars; 30 to 50 percent isn't uncommon.
While there's no replacement for displacement, modern engineering can help to seriously offset many of the big block's advantages without any of its weight or size restrictions. The fact is that these days, anyone building to over 500 horsepower is almost certainly using a power-adder like nitrous or a turbo, and a number of companies like Merlin, World Products and Dart offer aftermarket small blocks capable of over 400 cubic inches and 1,000 horsepower. What it boils down to is that unless you're running a Pro-Stock racer or have a particular love for big blocks, a small block will be lighter, cheaper and more practical.
