What is the difference guys?

 

Do you want actual math? One is bigger, and uses big block parts intead of SB parts. You can go with more bore and more stroke in a BB, but it costs more to build as well. It will also weigh ~200 pounds more, at least in full iron trim, IIRC.

As for priority main oiling etc, I dont know, so someone will specify more stuff for you I'm sure...

 

It would be nice to get into the tiny details of it... Lots of info to be learned and I did a search through google and got a bit empty...

The real question is what makes it a big block??? the bore size???

What would be the difference between a 427 big block and a 427 small block??

Is there is such thing as, "after x bore its considered big block" etc?

 

I always thought once a small blocks displacment surpassed 400 ci it is considered a big block.

 

no

Some things that i know are different are:

Wall thickness (even on 400sb)
weight
deck height
wider *i think*

 

The whole block is physically larger. There are SBC 400s that were used in trucks, you still see these today as 406s, 377 (destroked), 434 etc etc

So, the bore AND stroke is usually larger in a BB. 396(402)/427/454 were the "early" BB, before that there was the 409 and I unfortunately forget the other one (3xx?). Todays big blocks are different than the older ones, in at least cam design, and probably different internals as well.

Its definately not as simple as just bore being larger, so with that out of the way, it might be nice to know design differences, but then we will probably get into gen vs gen just like with small blocks.

 

the early BB you speak of are the 348,409, and 427 W head motors, i have a 348 if anybody wants one just pm me

 

Here's our answer. BB's have a larger deck height than SB's (to make it as simple as possible). Since the deck height is bigger, everything is bigger. Cubic inches has nothing to do with defining a BB or SB.

 

Other than the SBC and BBC are quite different designs, the big difference is bore spacing; the distance from the center of one cylinder bore to the next. SBC is 4.400 inches and I believe the BBC is 4.800 or so. Of course this allows for larger bores, and the taller deck on the BBC allows for longer strokes. This all adds up to more displacement available from a "Big Block". Sure you can stretch a SBC to 427 or 454 but you can stretch a BBC to 672 or more cubes. The LS1 shares the 4.400 bore spacing of the earlier SBC because the basic tooling to machine the engine block is built solidly at that spacing. Changing it in all existing SBC engine plants would be cost prohibitive.

SBC was popularly known as the "Mouse" when it first came out (1955) probably because it's stamped ball-pivot rocker arms (invented by a Pontiac engineer) seemed to be "Mickey Mouse" to folks used to cast or forged rockers on shafts (Ford, Olds Chrysler, etc.).

There's another story that, because the Chrysler Hemi was called an "Elephant" and SBC (Mouse Motors) were winning so many races, it was called "Mouse" because elephants are supposed to be frightened of mice. Who knows?

The BBC came along later and was called the "Rat" because it was bigger in almost every dimension than the "Mouse".

Some V8's like Pontiac had only one block size and one bore spacing, and had displacements from 287 to 455 cubes. The 301 of the late 70's was shorter and lighter, but still the same bore spacing. They were all "big blocks" if you've ever tried to lift one!

My old $.02

 

It is my understanding they have much larger heads as well. IOW, a 396 stroked SB and a 396 BB - the BB has much more potential because of there heads as compared to the mouse.

-Alex

 

Bigger engine needs bigger heads, runner volume, rocker arms, valves, cams, all bigger.

 

Not to get slightly off subject but I'll say it because stupid people always argue with me about this. Is a common misconception that the pontiac 400, 429, 455 and so forth models are big block. Well they arent all pontiac motors are on the same block. Actually although they wouldnt flow right at all you could probably put 329 heads on a 455

 

what about the oldsmobile 400cu.in. was that the same engine used in the pontiacs?

 

The Old's block is different than the Pontiac block. But, confusion may arrise because in 79 the T/A had an Olds 403 if it was an auto, and a true Pontiac 400 if it a 4-speed manual.

 

Yea Im not sure about the Olds and Buick 455's and such, they may be big blocks.