Is a Modern Hemi a big block or a small block?

[Jimmy N.]

I want my 6.2 to identify as a small block...in an effort to improve its mileage.

 

[1971demon]

What determines if a motor is considered a big block or not? I have a 5.7 R/T and my 6.2 SC. Are they big blocks or small blocks?

Ok...its been almost 5 hrs...nobody has come up with an acceptable definitive standard as to what qualifies as a big block.(at least by any automotive authority)...but we all seem to know what qualifies as a big block...reminds me of the guys hangin out togather down town sat nites..when the chicks walked by we couldn't define it...but we all knew a big ass...when one walked by...

 

[Hpindy]

The big block and small block are determined by physical dimensions and not cubic inch .

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[vortecd]

The big block and small block are determined by physical dimensions and not cubic inch .

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AGREED!

 

[Slowpoke387]

(Don't shoot the messenger...)

Pewpew

 

[Jack_Toepfer]

We have small blocks and big heads...
It’s not a displacement thing, you can punch an LS to 454+ cubes... our HEMI is right behind that... but they are not big blocks.

 

[jroyk]

I don’t know if there is an official definition, but to my mind, if the block can be bored (not stroked) to 7liters, it qualifies as big block.

 

[Hickster]

Back in the day, yesterday, we measured the big and smalls, yea, ask your wife. But up younder in Tenn it was the size of the tree you yanked it out of. Large tree, large block, veravvisa. Just don't be the shined out idiot looking for the crack in the oak tree. Then it didn't matter. No block,,, and a mess.

 

[BULL]

The big block and small block are determined by physical dimensions and not cubic inch .

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AGREED!

Starting with center to center cylinder spacing.

 

[Jack_Toepfer]

I don’t know if there is an official definition, but to my mind, if the block can be bored (not stroked) to 7liters, it qualifies as big block.

Interesting take on how the displacement is achieved. Does that apply to the small BBs listed on the first page? A ~350ish BB Mopar can be punched out to 7 liters?

 

[SilverBillet]

Interesting take on how the displacement is achieved. Does that apply to the small BBs listed on the first page? A ~350ish BB Mopar can be punched out to 7 liters?

I don’t remember ever discussing a 350 Mopar back in the day. The 361 and 383 were both B motors but a 383 was considered a big block by those Chevy guys. I thought that was funny but those SBC guys always used it as an excuse for losing to my 383 Road Runner! I never quite put it in the same category as a 413/440/426 even though I beat many of those. I’m just saying we always called them big blocks and a 273, 318 or 340 was a small block.

 

[jroyk]

Interesting take on how the displacement is achieved. Does that apply to the small BBs listed on the first page? A ~350ish BB Mopar can be punched out to 7 liters?

Not sure. I’m sure strokes are changed too, but I don’t think you can take a 318 to 440 ci or a 327 to 454. Got to have some cylinder wall thickness. At least, AFAIK. Not an expert.

 

[Jack_Toepfer]

Pontiac made a 350ci big block, was the same casting as their 455. Interesting.

 

[coolblue]

It's a very interesting question. In todays world nothing is a straight line or black and white, everything's a gray area. Back in the "old" days they physically wouldn't engineer anything over @350ci (with the exception of Pontiac) without going to a physically larger block. Generally. 350-400 was a middle ground and anything 400 or over was def big block. But today they have so many kits and options and bore, stroke, mix ,and matches that almost anything's possible. Is it a big small block or a small big block??? Honestly, I say small block.
P.S. It aint so big looking when you remove the plastic dress up covers. I all ready took mine off.

 

[Marc W]

Mine identifies as a big block.

 

[72 440 Barracuda]

Mine identifies as a big block.

I self identify as 707 hp - it doesn't matter how you are born these days - those are big numbers!
Actually I think it had more to do with cylinder bore spacing - larger spacing (bigger block) differentiated between the basic blocks used - the 318/340/360 had a smaller spacing than the 361/383/426/440 - AMC never had a big block or small block - all were the same basic block, but GM and Ford had a similar arrangement to Mopar. Big and small blocks...

 

[moparjim]

@SilverBillet the 350 cid b series big block was only '58 I believe then went to the 361.
@coolblue Chevy had a 400 cid small block
As @Jack_Toepfer mentioned the Pontiac but I'm pretty sure Olds and Buick were the same. Hell years ago my buddy borrowed a 307 intake from my 442 for his 455 motor to move his car around. 😳

 

[Hpindy]

Mopar big blocks

B series
350, 361, 383, 400

RB (raised block)
383, 413, 426, 440

Mopar small blocks

LA series
273, 318, 340, 360

Poly series
318


I'm 100% positive the mopar big block and small block are determined by physical dimensions. I went through my old mopar performance books and thats how they referred to them also .

The gen 3 Hemi has physical dimensions similar to the LA small block so I'm calling it a small block .

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[Hpindy]

I don’t know if there is an official definition, but to my mind, if the block can be bored (not stroked) to 7liters, it qualifies as big block.

No Mopar small blocks could be bored that large . The only Mopar big block that could be bored that large was the 413 ( the 426 was already 7 liters and the 440 was already larger ) .

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[jroyk]

No Mopar small blocks could be bored that large . The only Mopar big block that could be bored that large was the 413 ( the 426 was already 7 liters and the 440 was already larger ) .

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We agree, then.