Cubic inches

[King Dribble]

Just curious, at what level (in cubic inches) is the general cut off number between a small block and a big block??? Just wondering.

[Xauterus]

It is more to do with the block model rather than its capacity. A windsor can be 289, 302, 351 but can be takem to over 425cu but they are small blocks. FE were considered big blocks from 352 to over 400cu. The 385 series are the 460s and smaller are big blocks.
Probably all began with the physical size of the blocks when originally produced.

[MrEL]

Its not hard and fast.
A 396 Chev is a big block but a 400 Chev is a small block.

[smciner1]

The defining point is usually the Bore Spacing.

[Crazy Dazz]

Well, it kinda IS a hard rule. The BLOCK is the block, its one or the other.
The Windsor, Cleveland, and Modular (inc Coyote) are considered small blocks. The MEL and 385 were big blocks.
In answer to the OP's question, I suppose the changeover is somewhere around 400.
Some small blocks, such as the Chev and Clevo can go to around 400, usually with raised decks to accommodate a longer stroke. Big blocks typically start in the high 300's. A better way might be to look at the bore. Small blocks top out at 4 inches, and that's about where big blocks START.

[FPV GTHO]

Generally the Windsor and Cleveland/335 family engines are small block and the FE and 385 family engines are big block. There's also the older family engines that those 4 replaced. The newer engines don't really have a big block/small block distinction. Since the introduction of the 6.2 it's probably the first time since Ford dropped the 302 that they've had multiple V8 families. AFAIK GM kept things a lot simpler and as such they're cheaper to upgrade.

The smallest factory big block I know of is the FE family 352 and the biggest small block is the 335 family 400M. I've also seen the FE family refered to as more of a medium block.

[pottery beige]

you need big rocket covers

big blocks have big rocket covers

[Bossxr8]

I think deck height is a good indicator for wether it is a big or small block.

But the lines can get blurred, Ford Racing are offering 460 cubic inch Windsors now.

[BIONIC MAN]

do you think the OP is asking at what cubic inches the "cutoff number" is, thinking that a particular engine can become a big block when bored/stroked?
like a 302 Windsor is a small block, but a 434 Windsor is now a big block?

As has been said before its to do with bore spacing of the original block... not directly related to cubic inches.

[BIONIC MAN]

Originally Posted by pottery beige

you need big rocket covers

big blocks have big rocket covers

Sure.. like I need new SEAL panels for my car.. they must have got fully rusted out from the salt water with all the seals living in there!?!?

[pottery beige]

Originally Posted by BIONIC MAN

Sure.. like I need new SEAL panels for my car.. they must have got fully rusted out from the salt water with all the seals living in there!?!?

https://www.youtube.com/watch?v=ZUabDrfjATY

[XB GS 351 Coupe]

Originally Posted by pottery beige

you need big rocket covers

big blocks have big rocket covers

I am guessing they are covers covering the rockets rather than the much more common rockers.

[BIONIC MAN]

hahaha... now back to big block/small block discussion...

big block must have rockets under their covers.. that's why they go so fast.

[pottery beige]

i've still got icecream over my beak

[Crazy Dazz]

Originally Posted by Bossxr8

I think deck height is a good indicator for wether it is a big or small block.

Not really, the same basic block is often made with different heights. The bigger Clevos or "M" blocks had a 10.3 inch deck, the same as the 385 big block.

Originally Posted by Bossxr8

But the lines can get blurred, Ford Racing are offering 460 cubic inch Windsors now.

They're not actually Windsors, but yes it does show how the lines can be blurred with newer technology. Those "Man-O-War" blocks are externally compatible with Windsor fittings and weigh only 60kg more. So you can now get a "big block" in a small block package.

[Moby Vic]

Originally Posted by Xauterus

Probably all began with the physical size of the blocks when originally produced.

Correct. The terms "big block" and "small block" refer to the design rather than the displacement. Small blocks use thin-wall casting.

AMC offered a 390 and 401 that used the same block as the 360 and smaller variants (I can't remember the original displacement--327 or 343, maybe). It was a small-block engine with "big block" displacement.

[Bossxr8]

Originally Posted by Crazy Dazz

Not really, the same basic block is often made with different heights. The bigger Clevos or "M" blocks had a 10.3 inch deck, the same as the 385 big block.They're not actually Windsors, but yes it does show how the lines can be blurred with newer technology. Those "Man-O-War" blocks are externally compatible with Windsor fittings and weigh only 60kg more. So you can now get a "big block" in a small block package.

Its a Ford Racing 351 block.

And it's a straight Windsor.

http://www.fordracingparts.com/parts...KeyField=23194

[Charliewool]

Originally Posted by smciner1

The defining point is usually the Bore Spacing.

Correct!... In fact FE's are a "medium block".
Bore spacing is the only way to define "big block"/ "small block" in Fords.
Cubic inches and deck height are irrelevant.
Eg: Windsors were as small as 221cu and as large as 351.
FE's Started at 332cu to 428 with some odds in between like 406 & 410.
Won't even mention Y blocks (272, 292, 312 etc) which by bore spacing are "small block".. until you try and lift one!

[MethodX]

Originally Posted by MrEL

Its not hard and fast.
A 396 Chev is a big block but a 400 Chev is a small block.

396, 427, 454 are big blocks true.
The 400 is a stretched version of the 350 is it not?
But didn't Chevrolet still produce a 402 version of the 396 big block?

[GTP-RPD]

Originally Posted by MethodX

396, 427, 454 are big blocks true.
The 400 is a stretched version of the 350 is it not?
But didn't Chevrolet still produce a 402 version of the 396 big block?

I had read once that all 396's became 402's in 1970 but were called 396 for insurance purposes.

[MethodX]

Originally Posted by GTP-RPD

I had read once that all 396's became 402's in 1970 but were called 396 for insurance purposes.

Then you have the 348 and 409 big blocks. The w heads, Which were available until the mid 60's
Shes so fine my 409.....

[barnz_xr8]

its deck height and bore spacing, cubic inch's are irrelevant .

[Crazy Dazz]

Originally Posted by Bossxr8

Its a Ford Racing 351 block.

And it's a straight Windsor.

http://www.fordracingparts.com/parts...KeyField=23194

Nope.
Ok, that IS the Ford Racing Version, but the same thing applies. The one thing it definitely is NOT is a "straight Windsor."
It's a NEW speciality block which again is mostly externally compatible with Windsor peripherals. The deck height is higher again, and the material is a lot stronger (high Nickel content I believe) again allowing a larger bore.

[chevypower]

Originally Posted by Bossxr8

I think deck height is a good indicator for wether it is a big or small block.

But the lines can get blurred, Ford Racing are offering 460 cubic inch Windsors now.

GM Powertrain also has a 454 LSX (small block).

[Sox]

Originally Posted by smciner1

The defining point is usually the Bore Spacing.

This is the right answer.

[noflac52]

All of the engine displacement, deck height etc stuff is not really relevant. Its the weight of the block. You have to compare apples with apples and in the sixties and seventies they were made of cast iron and the big blocks weighed more than the small blocks hence big blocks, small blocks.
We aren't talking about engines here for those who will come back and say such and such engine weighs more than such and such engine. We are talking about blocks.

If a bigger displacement of more than 400cu in or so was required a bigger block was cast to build a bigger engine. With todays technology big block/ small block isn't as defined as it was then.

[pottery beige]

Originally Posted by noflac52

All of the engine displacement, deck height etc stuff is not really relevant. Its the weight of the block. You have to compare apples with apples and in the sixties and seventies they were made of cast iron and the big blocks weighed more than the small blocks hence big blocks, small blocks.
We aren't talking about engines here for those who will come back and say such and such engine weighs more than such and such engine. We are talking about blocks.

If a bigger displacement of more than 400cu in or so was required a bigger block was cast to build a bigger engine. With todays technology big block/ small block isn't as defined as it was then.

what are you on

[noflac52]

Facts

[FPV GTHO]

Of course, generally if you design a motor from scratch with a taller deck height and wider bore spacing it's going to weigh more. Both of those are needed for a wider bore and longer stroke. In a perfect world, each unique displacement would have a unique block casting, but that would be massively expensive, so you're left with manufacturers pushing the limits and getting small blocks matching and exceeding capacities of big blocks.

[GTB 351]

its bore spacing. 4.8 inches for hemi, 4.9 for 385 family, 3.84 for bb chev. Top fuel runs Hemi's because the rules limit you to 4.8 inches, not because they are the best! Most small blocks are around the 4.3's or less.
Deck height Phhhttt! big block chevs are 9.2 same as a clevo, 351 windsors are 9.5. Don't give a rats asse what a small block chev is coz I'll never touch one.
Then theres rod length - 5.7 for the bigger smallblocks [except mopar which are a bit longer] Big block fords and mopars are 6.6 inches plus, chevs a bit less...................................blah blah