Rd16rr

I know its a rookie style question...i never learned the full definition of small vs big block motors...i always related it to cubic inches

BEZ06

Small block

The 7L/427ci LS7 in the C6 Z06 and Camaro is a small block.

Take a look at this for a little more info:

https://answers.yahoo.com/question/i...8202935AASueGr

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ufaj26

Big Block Chevy From the old days: 454 cubic inches

BEZ06

CL !!!!

The old big blocks were a pretty massive architecture!!

That looks very similar to the big block 455 in my '70 Olds 442!

I don't think that would fit too well in a C6 or C7!!

Not to mention the additional weight it would add to the front of the car.

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JoesC5

Cylinder bore center to center distance defines a small block or a large block. Small block Chevys are 4.40" and big block Chevys are 4.84".

Since the current LS and LT series engine have the 4.40" bore centers, they are small blocks

Higgs Boson

the last time a big block was in a corvette was 1974, i believe.

http://en.wikipedia.org/wiki/Chevrolet_Big-Block_engine

NSC5

I believe the only BB engines now would come from the Performance Parts division. The last new vehicle usage I am aware of was the 8.1L version used in Chevrolet/GMC 3/4 and 1 ton pickups and I believe the Suburban may have gotten it for a few years but that was several years ago. They were also available in marine and industrial models but according to the GM powertrain site that is no longer the case.

Interestingly the "classic small block" 350 CID (5.7L) is still available for marine applications rated at 292 HP or in industrial versions running propane or NG rated at 216 and 196 HP respectively.

JoesC5

Actually, Oldsmobile and Pontiac didn't have "small" blocks or "big" blocks. All their displacements used the same block(with different bore diameters and strokes).

The Oldsmobile's 330, 350, 400, 403, 425 & 455 engines all were the same block(4.625 bore centers), and the Pontiac's 316, 326, 347, 350, 370, 389, 400, 421, 428 & 455 were also the same block(4.620 bore centers).

But, their external size(even the small displacement models) made them appear to be "big" blocks like the Chevy "big" Block, even though they didn't have as great of bore centers as the Chevy "big" block's 4.84". The Chevy "big" block came with 348, 366, 396, 402, 409, 427 & 454 displacements.

AZDoug

The 348 and 409 was totally different block, and no parts will interchange with the Mk IV 366, 396, 402, 427, 454, though the bore centers may have been the same as the MkIV BB.

Doug

BEZ06

Thanks - I've never had a big block then!!
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MavsAK

Good visual difference there.
You'll know a big block if you ever see one, especially next to a small block.

JoesC5

The 348 and the 409 had the same basic block as the MarkIV except for the decks being at an angle(74 degrees), to create a wedge combustion camber, since the heads did not have a combustion camber.


On the MarkIV they went back to the deck being 90 degrees to the cylinders and the heads had the wedge combustion chamber, but the engine design was based on the W engine other than the weird heads, and odd decks on the block.
Those changes came from the design of the MarkII Z11 427 mystery engine that was the W bock but had the 90 degree decks and the new heads had the combustion chamber in the heads.


Granted, that with the MarkIV engine in 1965, they raised the camshaft 1/8" and increased the camshaft journal diameter. In addition they increased the main bearing diameter over the W engine and the MarkII.

Still, the MarkIV was an evolution of the W engine and with the 4.84" bore center's the 348 and the 409 were "big" block engines.

camirocz

So now go put headers on your small block and go race that big block.Lol

VictorBarron

This is a 496ci engine with a ProCharger supercharger, and alcohol injection in my sons 68 Chevelle.



496

GOLD72

BINGO.

Unreal

Even with same bore spacing, I would say you have neither. Big block/small block refers to gen1/2 chevy v8 motors. Gen 3/4 are LS blocks, Gen 5 are LT blocks. You have a LT series motor, not a small block or big block.

Just like a coyote motor isn't a ford small block, it is a coyote motor.

JoesC5

Then what do you call an engine that is a LS6, or is a LS9 or is a LT5 in 1978?

In 1978 the LS6 was a L4 151 cu in 2Bbl engine and in 1978 the LS9 was a Gen1 350 cu in 4 bbl. and in 1978 the LT5 was a Engine Performance Pkg.-High Alt. In 2001, the LS6 was a "small" block in the Z06. In 2009 the LS9 was a "small" block in the ZR1 and in 1990, the LT5 was a "small" block in the ZR-1.

RPO designations have nothing to do with whether a Chevy engine is a "small" block or a "large" block.

Higgs Boson

no

yes

Unreal

My bad, but I still think calling them big/small block is a bit silly and out dated.

Then call it a Gen 5 motor. I think the small/big is just out dated and doesn't apply to the current 1997+ motors. Since there is no gen 4/5 big block why designate? Just call it a Gen IV motor, or Gen V motor, not a small block IMO.

onyx_z71

I can't speak for Pontiac, but there was an Olds small block and big block. The bore spacing may have been the same between the two, but the Olds 425 and 455 had a taller deck for the longer stroke which also required a wider intake manifold. I would consider that a big block compared to the 403 and smaller V8.