[rabrawlins]

Hi Guys,

Someone asked me a question the other day that stumped me good. What is a big block, what is a small block? I would like a proper definition so if anyone out there knows...

[72 chevy]

Hey Rab! I guess the simple definition is that a big block is physically larger than a small block, and is usually more cubic inches. If you want to learn a little more about v-8 blocks, check out www.hotrod.com Next to "stories" click on Basic Tech Series Cylinder Block. Theres some decent information there. Hope I helped a little!

[blown69stang]

Small blocks are generally considered less than 350 to 360 cubic inches. Big blocks are generally considered bigger. A 350 chevy and a 351W Ford are technically small blocks but with engines getting smaller and smaller like 2.4 to 3.8 litres rather than 5.0 and higher, some people not into racing call a 350 and 351W big blocks in respect to their import engines. Alot of times, small blocks in the same casting series can use the same motor mounts, heads, headers, and other items; as is the case with a 289/302 (same block different stroke) and the 351W Fords. Big blocks can by no means use the same hardware as small blocks because of size and power difference.

[jeff of nc]

simply put size of the block compared to other v-8 from the same manufactor. for instance chevy has made small blocks all the way up to 400 cu. in. and a stroker motor can be of even bigger displacement. on the other hand chevy also made 396 lg. blocks.
Pontiac, on the other hand, didn't make ether one, all there motors were just v-8's. externaly they are all the same.

[4 Jaw Chuck]

It seems that this issue gets rehashed every couple of weeks, here is how it has been commomly described.

-Big blocks have big block transmission bolt patterns.

-Small blocks have small block transmission bolt patterns (Hence your 727 Torqueflite trans will not fit on your 340 Chrysler because of the bolt pattern difference).

-If the manufacturer calls your engine a big block or small block the above does not apply.

It's about as clear as mud and matters about as much.

[rabrawlins]

Thanks for the replies but...I've been rodding for 30 years now and I've heard most of these explanations before. What I'm after is a "definition", something I can take to the bank. As to 4 jaw chucks comment, it does matter to me and your explanation of tranny bolt patterns kind of proves that it could matter a lot to anybody that's trying to do a mix and match, which I have a feeling happens a lot in this hobby. So if anybody can give me a real definition or point me to one I'd sure appreciate it.

Thanks All

[Shawn Asseln]

It is either bigger than most or smaller than most. Big and small. Most corporations used two basic design platforms for thier engines. one a smaller cube engine and the other a bigger cube engine. That is where big and small come into play. A big block is physically bigger as a small block is smaller.

[406 small block]

chevy made a small block engine from 265 CU IN to 400 CU IN they all so made big blocks from 400 CU IN up now to over 500 CU IN

[406 small block]

my mistake they started with I beleave a 396 big block

[mustang66maniac]

hows this for a definition:

Big Block- a large engine block

Small Block- an engine block smaller than a big block

[Chevydude]

Right on "stang66" you got it right!!!!

[78 monte]

Since the day I heard about the 427cu. small block stroker I lost track.Big,little motor/little,big motor/big,big motor/little,little motor? I think I need to lay down.

[30coupe]

I think 4Jaw was right. What good is a definition in trying to mix and match parts. You'd better KNOW what you've got before you buy parts, much less try to bolt them together. Otherwise, as the old Johnny Cash song goes: the transmission was a 53 and the motor turned out to be a 73 and when we went to put it together all the holes were gone. Just knowing if it is a big block or a small block still doesn't mean the parts are interchangeable (ie: vortec heads fit any small block, but just try to bolt an older intake to them!) Any definition would be worthless in matching parts. No offense intended.

[mpescatori]

Hi guys
I must say that Mr. 406 Small Block has got it right. In the days when cubic inches mattered more than mpg, and mpg lower than your golf handicap was a status symbol, US manufacturers simply made hi performance engines by building bigger and bigger engines, with displacement often larger than trucks in Europe!
So, (GM for one) manufacturers essentially made three engine types:
1) a 6-in-line for economy minded dudes,
2) small block V-8 for most general purpose cars
3) big block V-8 for hi-performance cars, limos and pickups

European manufacturers followed the same system, but with 4 cylinder engines, be they OHV or DOHC;
in any case, the top-of-the-line small block would generally have, fresh out of the factory, more or less same cu.in and HP as the basic big block, but weigh quite a lot less.