Big block/small block?
 

Quick question:

Hey, I hesitate to ask this question b/c somehow I feel I should know the answer, but it is one which I simply have never thought about.

When do motors become big blocks? I'll assume it is from the amount of liters or cubic inches-- once it passes a certain #, it's a big block? (I feel dumb asking this, but anyway, here it is). What distinguishes a big block from a small block?

Good question..basically what diminishes a small block from a big block is the size of the heads, stroke, bore, etc.

I always thought it had to do with the type of block used, ie the way the oiling system is set up, etc. Hot Rod built a big block and small block 400 or 350, which led me to believe it wasn't a straight displacement thing.
I've also seen the 351 C referred to as a big block, because its a part of the 335 motor family.

Let's hope Chris can clear this one up for us.

the 351 modified 400 is still a small block isn't it?

Big blocks of a given brand always have a bigger bore than small blocks of the same brand. If you stroke a small block to 400+ CI, it's still a small block.

I think it depends on what the manufacturer was (is) producing at the time. The engines are distiguished as "small" or "large" blocks. It really doesn't depend on the exact displacement.

A "small block Ford" could be anything from a 221 CI Windsor to a 400 CI Cleveland. The big block FE was a 352, 390, 406, 427, or a 428 CI engine. The 385 family were all "big blocks". 429 and 460's. There are some larger 385 family crate engines.

Rev

Displacement, bore, and stroke have nothing to do with it. Neither do the heads, or other bolt on parts. It is strictly the physical size of the bare block. Most manufacturers have 2 (sometimes more) sizes of V8 block castings, one smaller than the other. This is done so that the cooling jackets around the cylinders are never too far or too close, which would both lead to poor cooling.

For example, as mentioned, a Ford 352 is a big block, whereas a 400C is a small block. Set the two bare blocks next to each other, and you'll see that the 352 is physically bigger.

Take care,
~Chris

Ah ha!. The Wud of Pkr has spoken. :D (this is what we were waiting for--according to the prophecy)

Thanks for illuminating our feeble minds PKRWUD. :)

Chris is correct. it is psyical size. although one company of the V8's didnt have a "small" or "big" block and that was Pontiac. they all utilized the same block structure. Olds so called had a "small" and a "big" block, but mainly they just raised the deck height. the psyical size of a Olds 350 compared to a 455 Olds isnt that much different. just thought i would throw that in:)

That's exactly right. The difference between an Olds big block and an Olds small block is 1" in deck height. As a result, parts like heads are interchangeable, but intakes aren't.

:)

Take care,
~Chris

Little valves?
 

That's also why the Olds had little valves in the large displacement engines isn't it?

Rev

They didn't all have little valves. The "B" heads came from the factory with 2.072" intakes and 1.625" exhausts. Starting in 1973, however, the combustion chambers got bigger, and the valves got smaller, for emissions reasons. Still, even then the 455's had 2.000" intakes and 1.625" exhausts. Not huge, but they flowed very well. They also could be custom ground to accept larger valves.

Take care,
~Chris

One person told me that a way to tell the diff between a big and small, was the oil ports above the cam. Small block had small holes, and the big block had bigger-long holes.