Originally Posted by JORD88
I was wondering at what cc's/ liters does a small block turn into a big block? I'm guessing that a 5.7 liter is where a bigblock starts but I dont really know.
it has nothing to do with displacement but engine design architecture. And for the most part it is really referring to Chevy V8 engines, in the two primary modern engine families.
The "small block" Chevy V8 started out at 265 cid, and went up to 400 cid/6.6 liters (but can be bored and stroked to higher displacements). The "big block" Chevy V8 started at 366 cid and went to 454 cid in street form and 502 cid in crate engine form (and can be bored and stroked larger yet). The two engine families overlap in displacement, but are of different designs that are fairly interchangeable within the family. Anything in the small block architecture is a small block even if the displacement is up to 427 or more cid (7 liters, like the new LS7), and anything in the big block architecture is a big block even if the displacement is as low as the original 366 cid.
As far as architecture, the differences are primarily in bore spacing, port layout, and valvetrain layout. All big blocks will use one set of architecture and all small blocks will use another, hared within the family regardless of actual displacement.
Ford and Dodge V8s use different family designations, but also have roughly big and small block families, with more variations. For example, the Ford small block family is more accurately termed the Windsor engine family after the location of the engine plant that built them. They range from 221 cid to 351 cid,but can be stroked to 427+ cid if you start with the 351W block which is 1 inch taller in deck height. there is a mid block design, called the Cleveland/Modified, which includes the 351C/351M/400M. With a bit of work you can use the heads from these engines on the Windsor blocks. the factory effectively did that with the BOSS 302 engine (which is not the same as the Aussie 302 Cleveland, which is a destroked 351C). Then there are two modern big block Ford engine architectures, which range in displacement from 331 to 460 cid in stock form.
Confused? Remember this: displacement is not the determining factor in what makes a big block or small block. Architecture is.