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 Big Block vs. Small Block V8

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Rickw
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PostSubject: Re: Big Block vs. Small Block V8   Wed Dec 23, 2009 9:25 am

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.?????
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PostSubject: Re: Big Block vs. Small Block V8   Wed Dec 23, 2009 10:19 am

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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PostSubject: Re: Big Block vs. Small Block V8   Wed Dec 23, 2009 10:50 am

Quote :
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).

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PostSubject: Re: Big Block vs. Small Block V8   Wed Dec 23, 2009 11:20 am

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".
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PostSubject: Re: Big Block vs. Small Block V8   Wed Dec 23, 2009 11:25 am

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.
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PostSubject: Re: Big Block vs. Small Block V8   Wed Dec 23, 2009 11:33 am

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)?


Last edited by Rickw on Wed Dec 23, 2009 12:38 pm; edited 3 times in total
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PostSubject: Re: Big Block vs. Small Block V8   Wed Dec 23, 2009 11:49 am

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.
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PostSubject: Re: Big Block vs. Small Block V8   Wed Dec 23, 2009 11:52 am

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.
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PostSubject: Re: Big Block vs. Small Block V8   Wed Dec 23, 2009 12:08 pm

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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PostSubject: Re: Big Block vs. Small Block V8   Wed Dec 23, 2009 12:16 pm

Quote :
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.

_________________
'98 SC Riviera 268k miles 298 HP/370 TQ 0-60: 5.79s ET: 13.97 @ 99.28 4087 lb 20.1 avg MPG Nelson Ledges Lap: 1:30
3.4" pulley AL104 plugs 180 t-stat FWI w/K&N 1.9:1 rockers OR pushrods LS6 valve springs SLP headers ZZP fuel rails
KYB GR2 struts MaxAir shocks Addco sway bars UMI bushings GM STB Enkei 18" EV5s w/ Dunlop DZ101s F-body calipers
EBC bluestuff/Hawk HP plus SS lines Brembo slotted discs DHP tuned Aeroforce Hidden Hitch


'05 GTO 49k miles 0-60: 4.8s 16.9 avg MPG Nelson Ledges Lap: 1:26
Because fun


Last edited by AA on Wed Dec 23, 2009 2:47 pm; edited 1 time in total
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PostSubject: Re: Big Block vs. Small Block V8   Wed Dec 23, 2009 1:54 pm

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.


Last edited by L67 on Wed Dec 23, 2009 2:10 pm; edited 3 times in total
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PostSubject: Re: Big Block vs. Small Block V8   Wed Dec 23, 2009 2:08 pm

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.
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PostSubject: Re: Big Block vs. Small Block V8   Wed Dec 23, 2009 2:16 pm

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)
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PostSubject: Re: Big Block vs. Small Block V8   Wed Dec 23, 2009 2:19 pm

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.


Last edited by L67 on Wed Dec 23, 2009 6:00 pm; edited 3 times in total
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PostSubject: Re: Big Block vs. Small Block V8   Wed Dec 23, 2009 2:22 pm

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