Difference between a big block and a small block

My son asked me, "What is the difference between a big block and a small block?" I told him it was probably based on a lot of factors/criteria: minimum cubic inches, outer dimensions or shape of the block, location of the centerline of the crankshaft in relation to the block, etc. There may be no definitive answer and it may be up to the manufactures. Does anyone have a logical answer?

 

The size is where it starts.

 

If we're talking Chevrolets, then the heads and valve covers are the easiest way to spot the difference. That being said, there isn't much that is interchangable on the two engines. The big block block is longer, different balancers, waterpumps, intakes, oil pans--the whole enchilada.
Larry T

 

Originally when the car makers started building both small and big block engines it was so that their bigger, heavier cars would have sufficient power to move them, whereas a small block would have to work pretty hard. The fact the big blocks could produce more hp naturally led to their being transplanted into lighter bodies (ie GTO's, Chevelles, 442's, etc) which spawned the muscle car era. Big blocks generally make their hp down low and small blocks make theirs at higher rpms.

Don

 

It came down to what the big wigs of the detroit 3 said it was. Marketing power.

 

My son asked how come a Ford 332 V8 is considered a big block and a Chevy 400 is considered a small block? I told him it's kinda like families. Some familys have big kids and others have small kids. Still. I can't think of a clear answer he can comprehend.

 

The answer is that cubic inches alone do not determine if an engine is a big block or a small block, physical dimensions externally usually is the criteria. For example, there are now some 427 small blocks being built due to strokers, but the external size is still small block.

Don't look at the displacement, look at the outside dimensions.

Don

 

cylinder bore spacing

 

That's a pretty good explanation. The 332 is the smallest member of the FE family with the largest being around 428. The 400 is the largest of the small block Chevrolet family that starts at 262.
Larry T

 

I was told by an old drag racer as a kid that the main difference between a small block and a big block is that if you build the small block to compete with the big blocks and race big block cars all season at the end of the all thats left is powder.....

 

1 engine you can Carry in your Arms & the other you
need a Shopping Cart!

just my 3.5 cents

 

small block =$$$$ big block =$$$$$$$$$$$

 

Here is a picture of a big block vs small block Chevy engines. Both could be 427 cubic inches, due to a stroker crank being put in the small block, but it would still be a small block due to the outside dimensions.

If he still doesn't understand, do what I did with my kids. Tell them that is just the way it is.

Don

 

The biggest basic difference between a big block and a small block is the size and shape of the block itself. Cubes have little or nothing to do with it.

 

If you look at a car with a Chevy or Ford small block and then the same brand big block you will see the physical difference. Small blocks are small, and big blocks are bigger. It really is as simple as that. The terms identify the engine type, not cubic inches. A 352 Ford engine is noticeably bigger in external dimensions than a 351 Ford, and a 396 Chevy (big block) is noticeably bigger than a 400 Chevy (small block).

Next time you're at a car show, point them out and he'll get it.

 

Big block& small block in my guestimation probably originated with what people started CALLING their Chevrolet engines. IDK what GM called the SBC, but when the big block came out, people CALLED it a big block because the block was simply bigger.

The small block Chevrolet was introduced in 55, and in production trim displaced between 265 ci, and 400 ci. (I think there was a short lived Smogger motor that was what a 262 or something)

The Big block Chevrolet was designated the Mark IV upon its introduction in 64 (i think) and the latest revision was the mark V. It's stock displacement was between 366 to 502. (There was also the 348/409 series introduced in about 62 which should probably be considered the original Chevy "big block", but they are usually known by their cubic inch designation).

As stated, the SBC and BBC shared a lot of common architecture, but few interchangeable parts.

I don't think there were "big block" and "small block" Fords, Chryslers, etc until the common Chevy designation became kind of generic, and was hung on other engines.

 

What this guy said!

Bore spacing is how it was determined!

 

Don's Hot Rods post #14 says it all in one photo. the physical size of the block it's self. When you see the two no matter what brand sitting side by side it makes easy sense.

Some small blocks had more cubic inches than some of the same brand's big blocks so cubic inch displacement doesn't have much if anything to do with it.

Some of these guys try to make it way to hard to understand trying to get their engine knowledge creds in.

 

Who knew I thought ceberus was going to get torn a new one here. It is nice to see fellow hambers taking the time to explain the differences so both he and his son have a better understanding. Kuddos guys keep sharing.

 

You are on the right track,

Think of it this way.

When a manufacturer creates an engine they just that, an engine
Conversely, when your mom and pop have a son they have just a son
When the manufacturer wishes to have and manufacture an additional engine then they must designate one as big and the other as small just as Dad would tell you to get your little brother.

-It is the fact that there are 2 engines that cause the manufacturer to have to designate just as your pop has to designate that one son is the little brother of the other.

In other words, if you only had one son you wouldn't need to designate or use the term little/big brother but the fact that a manufacturer (or your pop) decides to asd another sibling to the lineup forces them to designate.

-You could not have a big block unless you already had a small block in the lineup just as you could not have a little brother without the bigger version.


In respect to size/cubes.

There is no correlation as to cubic inches or height width or bore that designates ANY motor as a big or small block.

The fact is that you cannot have a designation for a big block unless you have a small block already in the line up.

So it is not a cubic inch or weight/width/bore/size thing, merely it is a term to differentiate between 2 siblings.


It's as simple as that and no more.


.

 

When it comes to installation the beauty of a Chevrolet engine is that no matter whether the engine is a small block V8 or a big block V8 starting 1955 they all fit in the same holes with the same motor supports in the same place. You have to move the radiator forward etc. but there is no firewall clearance problem in anything that had a V8 or 6 stock.

 

It's like Santa Claus and the tooth fairy, there is no such thing (wink, wink)

You'll notice most of the explanations on here are non-Ford. Ford engines are cl***ed as families. Even tho the last few years has seen an increase in usage of sbf to designate the windsor engines, us old guys still think of bb/sb as Chevy terms.

 

Be sure to tell him about the pontiac family. 1955 287 cubic inches to 1979 455 cubic inches and everything in between all in essentially the same size package. There are no big or small block pontiacs, EVER!!

I'm still trying to figure out the R B RB LA mopar stuff.lol

 

Well I geuss one has a big block and one has a small block

 

It's just a convenient way to distinguish one model of engine from another. Usually used for Chevrolet. As others have pointed out, a "small block" could be as big as 400 cu in, a "big block" could be as small as 366. But from a design standpoint they are still "small block" and "big block".

Chrysler used different descriptions, A and LA for their "small blocks" B, RB and Hemi for their "big blocks".

Other car makers used other systems. Pontiac, Buick, and Oldsmobile made engines from 350 to 455 cu in all based on the same model of engine (but different for each company) so they never used the terms "big block" and "small block" even though they made motors "big" and "small".


For those who want more detail on the Chrysler engine lineup. the A engine was the Polysphere small engine most commonly a 318 cu in, used in Plymouth and Dodge cars and Dodge trucks 1955 to 1966. The LA was a redesigned A engine with new wedge heads on basically the same A block, introduced in 1964 as a 273 for Valiant, Dart and Barracuda then expanded to a 318 to replace the Polysphere 318 in larger cars Continued into the 90s and built as a 318, 340 and 360.

Chrysler B engine, a bigger displacement engine introduced in 1958 to replace the hemi. At first the B engine was built in 350, 361 and 383 cu in form for Plymouth Dodge and DeSoto, with the RB being a "raised block" engine with decks 1" higher made as a 383 and 413 for Chrysler.

Soon the 350 B and 383 RB were dropped and 361 B, 383 B, and 413 RB engines were the rule. Followed by 426 and 440 RB engines.

The race hemi was a heavily modified RB block with new Hemi heads. The block was so modified, it will not interchange with an RB block. For one thing the Hemi got an extra row of head bolts.

Hope this helps clear things up.

 

It is about size, but not cubic inches. The size of the block is dictated by the distance between the bore centers. A small block Chevy, for example, (if memory serves) has the cylinders set 4.25 inches apart. This usually means about a 4" maximum bore, or a few thousandths over. The big block has a 4.5" distance between centers, which means a 4.25 inch maximum bore. When you lay out the engine using those centers, the big block ends up being two inches longer, which also translates into being wider and taller also.

Each manufacturer has variations on this. Chevy has used the small block configuration to build a variety of engines from about 265 ci to 427. The bores vary a little, and the strokes a lot. Each engine manufacturer "independently" ends up with about the same displacements, using very close approximations of bore and stroke.

 

While the blocks shown in the posted photo are both big-blocks - the one on the left is a raised deck aftermarket Merlin block, while the other is OE - the comparison between the size to determine terminology is still valid.

 

Thank you Moe for the correct answer...

Thank you for setting the record straight.

 

a picture is worth a thousand words

 

I was always under the impression it was the deck height


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