[bfrett123]

Can someone tell what determines a small block from a Big block? I know it's not the cubic inches because a Chevy 396 is a big block and 400 or 427 can be a small block. Is it the height of the block or the maybe the bore size? No one seems to be able to give me an answer!

[killerformula]

first of all, lets just talk chevy (lest somebody accuse me of not knowing the difference between a 383 big block chrysler and a sroker small block chevy).

There's a long list of "smallblock" chevy motors: 265 267 283 302 305 307 (don't get confused also an olds motor) 327 350 383 (comon stroker) and 400. These motors all look exactly the same from the outside (well, the 265 doesn't have an oil filter, minor differences). The block demensions of these motors are all identical. The bore and stroke of these motors makes the difference in CID, but they share a common "block." That's not to say you can take a 265 and bore it to a 400, castings are different, but like I said, block dimensions are the same.

Bigblock motors are a larger block, mainly for the purposes of being able to put more stroke and more bore into a given chunk of iron (without getting thin, weak areas or bores that are getting dangerously close to water jackets). Given the more spread design of the bigblock bores, the head design is much better than the standard smallblock. Bigger, better angled valves and intake runners can be used with bigblock motors, the bigger bores reduce valve shrouding. Bigblock is a more "performance" oriented design.

K

[Jared]

dont forget 377.

[poncho62]

Square valve covers, 4 bolts ............pre 88 Small block

Square valve covers, 2 bolts in middle of cover.......post 88 Small block


Larger, rounded valve covers.......7 bolts...............Big Block.

OR........................look up the engine numbers