Difference between big and small block?

[jlobbia]

What is the difference between big block and small block engines? I have been in nitro for quite a while but never really got a clear answer. Thanks.

 

[Rolex]

The size of the block.

Jeez, I'm an idiot. Same as car engines, big block has a longer piston stroke and more low end torque. Small block is a shorter stroke with more RPMs on the high end. Different gear ratios for maximum performance.

 

[olds97_lss]

The crank case is longer and wider physically. Carb is typically larger on a big block as is the exhaust port.

This is an old photo I had of a Omega 21 big block (top) and an OS 18 small block (bottom):

 

[jlobbia]

The crank case is longer and wider physically. Carb is typically larger on a big block as is the exhaust port.

This is an old photo I had of a Omega 21 big block (top) and an OS 18 small block (bottom):

Is there a point in size where it's defined as a big block? Like everything after .19 is a bb, and everything before is a sb?

 

[D3MON]

Typically
.12 (2.0CC)-.20 (3.3CC) is small block
.21 (3.5cc) and up to .36 (5.9CC) is big block
.37 and up is kind of a specialty category, mounting is typically different than the standard sized for big blocks.
as usual in RC there are exceptions, like the O.S. .21TM, its a big block internals with a small block case.
Picco .26max and a few other ones that i can't recall, are was what is called a "Mid-Block", small"er" block, case with big block internals.