What makes a Small block a Small block and a Big Block a big block?

[Unit 5302]

The 361 in the school bus is a 4.0469x3.500 bore x stroke. What kills it's rpm capability is a 2bbl carb, and 8.5:1 compression. It's not meant to rev, athough if there were to be a high po intake, better pistons and rods (the crank is already forged), and some compression, it'd probably wind over 5000 pretty easy.

Big blocks are heavy, bulky, and as a general rule high rpms meant 5500rpm-6000rpm. The 427FE was as rev happy as you could get in the FE line, and it redlined between 6000-7000rpm depending on how it was built.

There are several series of engines. External block dimentions were how they were designated big block/small block. Ford used a couple different sized blocks in the lineup for many years.

FE
385 series
MEL series

Those were the big blocks.

Y Block
Windsor or 90*
335 series

Those were the small blocks.