A style of Chevrolet, Ford or Mopar motor. American car makers are known to have small and big block V8 motors. Big block motors are more rare and powerful, but small block ones can be found easily and are cheaper to upgrade and own.

It is called a small block because literally it is a smaller block than the big block, go figure. Bearing nothing towards the potency of the motor, a small block engine can produce hundreds and in some cases thousands of horse power and be in stout competition with their bigger brothers.

Typical sizes:
Chevrolet: 283,305,307,327,350,400
Ford: 289,302,351Windsor,351Cleveland,360,400
Dodge/Mopar: 318,340

There are dozens of sizes of these motors, i would not likely be able to list them all, but those are just a few.

An interesting and pleasant note, the Chevrolet small block motor are actually 90% compatible with eachother. Example, a 350 intake manifold would bolt on perfectly to a 305. Sadly, the other car makes dont boast this feature. However on further testing, one can find that a Ford 302 will accept Ford 351 windsor heads thus making it a more powerful motor.