Big Block vs. Small Block V8

I've heard the term Big Block and Small Block used on 350's before.
What's the criteria for determining if a lower end is a Big block or a Small block.?????

easy way to tell if its a small block or a big block. is to look at the tubes on the headers coming off the head. on a big block they should all be evenly spaced and on a small block the 2 middle tubes will be really close and the 2 outsides farther apart from the middle tubes. on a Chevy anyways.

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I've heard the term Big Block and Small Block used on 350's before.
What's the criteria for determining if a lower end is a Big block or a Small block.?????

Small block and big block deck heights and main/rod diameters are different. Small blocks have smaller journals and a short deck height. Small and big block heads will interchange, but they don't always create compatible compression ratios.

Besides the above, a SBC isn't just a small CID engine. It is lighter, more efficient, and often not as durable as a big block. SBCs can be as large or larger in displacement compared to big block (427 Z06), and because of the newer/better materials, SBCs often create higher HP than a big block.

Probably the biggest difference was the intent behind the two types.
Big blocks were originally intended to make gobs of torque to move heavy cars and trucks, and were typically heavy and made to run very smooth. Also very long-lasting and reliable engines. Not for hot-rodding, but it can be done (aka 455).

Rickw wrote:

I've heard the term Big Block and Small Block used on 350's before.
What's the criteria for determining if a lower end is a Big block or a Small block.?????

Are we talking about Chevy's here?

Never heard of anyone referring to any 350 as a "big block".

In 1968 the 326 was replaced by the 350, which used a 3 7⁄8in bore and 3 3⁄4in stroke for a total displacement of 353.79 cu in (5.7976 L) although it was still called a 350 (5.7 L). This engine was offered in both 2bbl and 4bbl variations similar to the previous 326 engine. In 1968 an HO option was available in the Tempest and Firebirds that was rated at 320 HP. This engine was also offered in 1969 along with a second HO version. The later 350 HO was rated at 325 HP and was equipped with the 400 CI heads and the 400 HO camshaft. One of Pontiacs best kept secrets, this engine was a very hot setup in the Firebirds.
My brother had a Pearl white 1970 Firebird with the Big block 350HO. Nice car.

AA wrote:

Small block and big block deck heights and main/rod diameters are different. Small blocks have smaller journals and a short deck height. Small and big block heads will interchange, but they don't always create compatible compression ratios.

Besides the above, a SBC isn't just a small CID engine. It is lighter, more efficient, and often not as durable as a big block. SBCs can be as large or larger in displacement compared to big block (427 Z06), and because of the newer/better materials, SBCs often create higher HP than a big block.

Probably the biggest difference was the intent behind the two types.
Big blocks were originally intended to make gobs of torque to move heavy cars and trucks, and were typically heavy and made to run very smooth. Also very long-lasting and reliable engines. Not for hot-rodding, but it can be done (aka 455).

In your first sentence you mention that a Small Block engine will have a shorter deck height.
That would calculate to mean that it would have to be a short stroke, higher RPM engine.?
And is that the primary reason how you can ascertain that a Small Block will not be as durable.?
Am I correct in saying that the major difference between one engine being called a Small Block and the other being called a Big Block is the difference in stroke and as you mentioned different diameter crank journals. (with Cubic Inch Displacement being the same)?

a short block is a term used for a "Gopher" engine or reman engine without heads, intake, etc. The term long block refers to the same but including headz.

Hometown Hero wrote:

a short block is a term used for a "Gopher" engine or reman engine without heads, intake, etc. The term long block refers to the same but including headz.

This i knew, but I was trying to determine how to ascertain how one engine with the same cubic inch displacement can be called a Small Block or a Big Block.

Note: I made the correction to my previous post. I used the word Short instead of Small. My mistake.

Np, just wasn't sure if you were confusing yourself on this 1 or what? The Big block is essentially just that a "Big block", they're huge! A 350 Big Block from what I remember (its been about 10 years since my bro parted ways with his 1970) they are basically identical looking to the 427. Small block well opposite. They threw 400 BB headz on it and a 400 BB crank changed the bore n stroke. If you read my previous post it explain how they calculated it to be a 5.7L or 350 cid.

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In your first sentence you mention that a SB engine will have a shorter deck height.
That would calculate to mean that it would have to be a short stroke, higher RPM engine.?
And is that the primary reason how you can ascertain that a SB will not be as durable.?

I believe yes, the smaller deck height (distance from top surface of block to piston crown at TDC), would enable the SBC to rev higher due to less reciprocating mass. But I am not 100% sure, as I don't build these engines. If true, it would be a factor for durability.

Also, big blocks have more block material between cylinders, making the big block more robust and easier fit cooling passages (imo). For example, the recent Corvette Z06's 427 "small block" had made the cylinder walls so thin that they could not use that engine for supercharging (would not support the high compression); they had to change the design for the new ZR1.

There are probably some other reasons why the big blocks are near indestructible. Mostly, it was the fact they were designed for torque, smoothness, and durability, not ultimate power output, that makes the big block what it is. And there were exceptions where big blocks were used in performance applications, but ultimately the small block was the lightweight/high output platform that most sports/race cars ended up using under the hood.

Hometown Hero wrote:

In 1968 the 326 was replaced by the 350, which used a 3 7⁄8in bore and 3 3⁄4in stroke for a total displacement of 353.79 cu in (5.7976 L) although it was still called a 350 (5.7 L). This engine was offered in both 2bbl and 4bbl variations similar to the previous 326 engine. In 1968 an HO option was available in the Tempest and Firebirds that was rated at 320 HP. This engine was also offered in 1969 along with a second HO version. The later 350 HO was rated at 325 HP and was equipped with the 400 CI heads and the 400 HO camshaft. One of Pontiacs best kept secrets, this engine was a very hot setup in the Firebirds.
My brother had a Pearl white 1970 Firebird with the Big block 350HO. Nice car.

Right thats for the Poncho 350, the Chevy actually was 350ci with a 4.00" bore and a 3.48" stroke.

Rickw wrote:

In your first sentence you mention that a Small Block engine will have a shorter deck height.
That would calculate to mean that it would have to be a short stroke, higher RPM engine.?

This is partially true, in stock form you can make this assumption since the 454 and 455 made 500 lbft and 510 lbft respectively, while the 350 made ~360 lbft. This can be partially attributed to the stoke advantage (3.90" on the Buick and 4.00" on the Big Block Chevy) but the extra cubes also equal torque by default. The small block can get some awesome torque numbers with the 383 stroker package (.030" overbore, 400 ci Chevy Small Block crank (3.75" stroke)), and overcomes its inherent "short stroke" limitations. The block must be slightly clearanced for this swap however to prevent the rod bolts from contacting.

Things sure are different in the GM world. In the Mopar world the 340 was the only performance small block. The real performance muscle car engines were the 440 and 426 Hemi. If you talk about engine building on a Mopar board, they'll tell you to build the biggest motor you can get your hands on.

AFAIK the difference between a small block and big block, traditionally, is the distance between the piston cylinders, not deck height. More power would be created by larger displacement, and displacement would be increased by boring out the diameter of the piston cylinders. On a small block engine, you can only take this so far before running out of cylinder wall. Hence the need for the big block engine, which externally is a noticeably larger engine.

More recently "stroker" engines have become popular, which increase displacement by increasing the length of the piston stroke within the cylinder (if I understand it correctly). This allows small blocks to achieve displacement similar to smaller big blocks. Of course you can also build stroker big blocks with even greater displacement! But not many people need 1000+ hp motors in their grocery getters.

L67 wrote:

This is partially true, in stock form you can make this assumption since the 454 and 455 made 500 lbft and 510 lbft respectively, while the 350 made ~360 lbft. This can be partially attributed to the stoke advantage (3.90" on the Buick and 4.00" on the Big Block Chevy) but the extra cubes also equal torque by default. The small block can get some awesome torque numbers with the 383 stroker package (.030" overbore, 400 ci Chevy Small Block crank (3.75" stroke)), and overcomes its inherent "short stroke" limitations. The block must be slightly clearanced for this swap however to prevent the rod bolts from contacting.

So, is the 350 in this example a small block or a big block. It's still clear as mud to me.
Sorry, I seem to be slow catching on to the true definition of each (Small or Big)

Rickw wrote:

L67 wrote:

This is partially true, in stock form you can make this assumption since the 454 and 455 made 500 lbft and 510 lbft respectively, while the 350 made ~360 lbft. This can be partially attributed to the stoke advantage (3.90" on the Buick and 4.00" on the Big Block Chevy) but the extra cubes also equal torque by default. The small block can get some awesome torque numbers with the 383 stroker package (.030" overbore, 400 ci Chevy Small Block crank (3.75" stroke)), and overcomes its inherent "short stroke" limitations. The block must be slightly clearanced for this swap however to prevent the rod bolts from contacting.

So, is the 350 in this example a small block or a big block. It's still clear as mud to me.
Sorry, I seem to be slow catching on to the true definition of each (Small or Big)

The 350 is a Small Block. The Chevy 283, 302, 305, 307, 327, 350, and 400 were the OEM small blocks, while the 396, 402, 427, 454 and much more recently the 496 represented the Big Blocks. This is post W-series engines (348 and 409), used in the early 60s Impalas.

Thanks for all the info.
Was something I've been a bit confused about for quite some time.
Especially the 400 ci Small Block.

You're right, distance between the cylinder is usually greater too.

Actually the 400sbc I think all have siamese cylinder boreing so the water jackets around the cylinders actually touch each other. I think that's a pretty good indication that that motors not getting any bigger, at least not by boreing. I wanna say the LSx motors all kind of have that design to them but with high strength sleeves which is why you never really bore them out. They are stroked all the time.

Chevrolet never made a "Big Block 350" it was a pontiac engine solely used in Pontiac cars. I think your confusing the 350 chev small block, you can use 400cid small block headz and crank in the small block chev 350 but I have never found any history pertanent to Chevrolet and a BB 350. But I have been wrong before post me a link on some info I'd be interested to read up on it.

That Pontiac block is an amazing block it can be bored and stroked to just over a 455. The 455 Olds was a nailhead block so they are different designs, my buddy has the W30 455 in his 1967 442 awsome engine as well. But the simple fact you can get 455+ cubes out of a 350cid block is astounding imo. I doubt engine life would be as astounding maxing everything out like that, but once your talking about doing that stuff I don't think your worrying about longevity.

Hope we answered all your questions rickw. Muscle cars are kinda my thing, the Rivi has its own place in my heart tho.

Hometown Hero wrote:

Chevrolet never made a "Big Block 350" it was a pontiac engine solely used in Pontiac cars. I think your confusing the 350 chev small block, you can use 400cid small block headz and crank in the small block chev 350 but I have never found any history pertanent to Chevrolet and a BB 350. But I have been wrong before post me a link on some info I'd be interested to read up on it.

That Pontiac block is an amazing block it can be bored and stroked to just over a 455. The 455 Olds was a nailhead block so they are different designs, my buddy has the W30 455 in his 1967 442 awsome engine as well. But the simple fact you can get 455+ cubes out of a 350cid block is astounding imo. I doubt engine life would be as astounding maxing everything out like that, but once your talking about doing that stuff I don't think your worrying about longevity.

Hope we answered all your questions rickw. Muscle cars are kinda my thing, the Rivi has its own place in my heart tho.

I never said there was a Big Block 350, i was just adding to your story on the Pontiac 350 and showing how the Chevy design was completely different.

Sorry for the misunderstanding wasn't trying to offend you. Just thought we were talking BB's.

Hometown Hero wrote:

Sorry for the misunderstanding wasn't trying to offend you. Just thought we were talking BB's.

No biggie

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Things sure are different in the GM world. In the Mopar world the 340 was the only performance small block. The real performance muscle car engines were the 440 and 426 Hemi.

I think MOPAR used larger engines than anyone else for racing applications.

The new ZR1 (LS9) engine uses an LS3 block, which is more like a SBC than a big block, but it's technically neither. It's a totally new design that improves on the disadvantages of the SBC (like the thinner cylinder walls).

AA wrote:

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Things sure are different in the GM world. In the Mopar world the 340 was the only performance small block. The real performance muscle car engines were the 440 and 426 Hemi.

I think MOPAR used larger engines than anyone else for racing applications.

The new ZR1 (LS9) engine uses an LS3 block, which is more like a SBC than a big block, but it's technically neither. It's a totally new design that improves on the disadvantages of the SBC (like the thinner cylinder walls).

You guys are forgetting the about the Yenko Corvettes and Camaros that ran the all aluminum ZL1 427. It was a grotesquely underrated engine at 425bhp which its actual output is said to be between 500-580bhp. Then in the Chevelles GM produced the infamous LS6 454. The LS6 is another landmark BB in GM's line up along with its cousins the 455 Rocket Olds and the rare old Pontiac 428 which was only produced by GM for a short time.

Not forgetting those (big blocks are great street muscle engines), just saying the SBC is more common for racing. Lots of parts available. You can shove a 572 crate motor into your car of choice and tear up the street, but for modern racing, I've seen SBC-based designs on the track.

Maybe GM had just as many big blocks as Chrysler for NASCAR vehicles back in the day. I just think of Chrysler more because the 426 Hemi was a strictly race-bred big block that is still in wide use today (top fuel, not the modern SBC Hemi).

The ZL1 was strictly bred for racing, hence the all aluminum contruction. The street version was the cast iron L88 which my uncle Elmer has in his 69 Stingray convertable. Pound for pound the ZL1 would beat the pants off a Hemi all day long. Not to say you couldn't run a ZL1 on the street a few guys did but the L88 was much more popular. The ZL1 is as far as I know still available today in crate form, rated @ 430hp/450tq.

Hometown Hero wrote:

AA wrote:

Quote :

Things sure are different in the GM world. In the Mopar world the 340 was the only performance small block. The real performance muscle car engines were the 440 and 426 Hemi.

I think MOPAR used larger engines than anyone else for racing applications.

The new ZR1 (LS9) engine uses an LS3 block, which is more like a SBC than a big block, but it's technically neither. It's a totally new design that improves on the disadvantages of the SBC (like the thinner cylinder walls).

You guys are forgetting the about the Yenko Corvettes and Camaros that ran the all aluminum ZL1 427. It was a grotesquely underrated engine at 425bhp which its actual output is said to be between 500-580bhp. Then in the Chevelles GM produced the infamous LS6 454. The LS6 is another landmark BB in GM's line up along with its cousins the 455 Rocket Olds and the rare old Pontiac 428 which was only produced by GM for a short time.

The Yenko Camaros never actually received the aluminum ZL1 Rat, rather running the iron L72 427. The ZL1 only appeared in 69 1969 Camaros to comply with Super Stock homologation rules.