What constitutes a "small block" engine?
Thread Starter
Melting Slicks
Joined: Jan 2003
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From: Shreveport LA
LA Events Coordinator
What constitutes a "small block" engine?
Yesterday I saw a TV program where they kept referring to the "400 small block". I always thought that a 400 cid would be a considered a big block. So, what constitutes a small block engine? Enquiring minds want to know....
Racer
Joined: Feb 2008
Posts: 497
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From: Streator Illinois
The 400 is actually the same design as the first Chevy V8 of 265 c.i. and all the similar designs in 283,302,305,327,350, 400 and a few oddballs such as the 267? and 307 are also the same basic configuration and design. Many parts such as heads are interchangeable on these engines and these are referred to as Gen 1 engines
Big blocks such as 396, 427, 454 are a totally different animal.
Many later engines such as the LT used in Corvettes staring in '97 and later LS are also regarded as small blocks but as Gen 2 or Gen 3 engines and parts are not interchangeable between these and the Gen 1.
I probably forgot to mention a few things and I'm sure someone can chime in and correct me or elaborate.
Terry
Big blocks such as 396, 427, 454 are a totally different animal.
Many later engines such as the LT used in Corvettes staring in '97 and later LS are also regarded as small blocks but as Gen 2 or Gen 3 engines and parts are not interchangeable between these and the Gen 1.
I probably forgot to mention a few things and I'm sure someone can chime in and correct me or elaborate.
Terry
Race Director
Joined: Jul 2001
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Chev engine blocks came in two different external sizes- a big one and a little one. Nothing to do with displacement. The little one was used to make engines from 265 to 400 cu. in. and the big one from 366 up to 572.
Burning Brakes
Joined: May 2009
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From: Tucson AZ
St. Jude Donor '12
Burning Brakes
Joined: Sep 2011
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There are also tall deck small block gen 1 motors up to 473 cu inches and LS tall decks to 502. Big blocks now go out to 650 cu inches or more. I just installed a SBC 427 in my C2 rated at 556hp. The options and variations available today are amazing, with 20 different ways to get 500hp or better.
Burning Brakes
Joined: Dec 2010
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From: Winston Salem NC
I learned that anything 350ci and below was a small block. The 400 is an exception, but generally as you go bigger you need different block architecture to and handle the cubes and power.
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Melting Slicks
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From: Halifax, Nova Scotia, Canada
Race Director
Joined: Jan 2000
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From: San Jose CA
As far as gas V8s go, Chevy has had the W block (348/409), small block (265, 283, 302, 305, 307, 327, 350, 400 and a few others), the MKIV big block (396, 402, 427, 454) some other variants of the big block (496), the LT1 series (305?, 350) and the LS series (4.8, 5.3, 5.7, 6.0, 6.2, 7.0).
The gen 1 small block family is generally identified by 5-head bolts per cylinder, fuel pump fittings, motor mount style, distributor hole in lifter valley, siamesed center exhaust ports, coolant running through the intake manifold.... and some other characteristics I can't remember.
The gen 1 small block family is generally identified by 5-head bolts per cylinder, fuel pump fittings, motor mount style, distributor hole in lifter valley, siamesed center exhaust ports, coolant running through the intake manifold.... and some other characteristics I can't remember.
Pro
Joined: Aug 2000
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From: Vancouver B.C.
Just to make things more confusing,
sometimes a 400 is a Big Block !! ??
In the early '70s Chevrolet bored their factory 396s out an additional .030, so they became 402s.
However, for passenger applications such as Chevelles in the early '70s, they continued to call the 402 a 396 for marketing reasons.
But for pickups, why I am unsure, the trucks were badged 400, not 402 or 396. I just seen one of these the other day at a show 'n shine. A factory 402 BB, but badged 400. Can be confusing.
The BB also came as a 366, but these are tall truck blocks having a higher deck than the passenger BBs. They also made a 427 Tall truck BB. You find these 366 and 427 TT in medium size trucks such as school buses, etc.
sometimes a 400 is a Big Block !! ??
In the early '70s Chevrolet bored their factory 396s out an additional .030, so they became 402s.
However, for passenger applications such as Chevelles in the early '70s, they continued to call the 402 a 396 for marketing reasons.
But for pickups, why I am unsure, the trucks were badged 400, not 402 or 396. I just seen one of these the other day at a show 'n shine. A factory 402 BB, but badged 400. Can be confusing.
The BB also came as a 366, but these are tall truck blocks having a higher deck than the passenger BBs. They also made a 427 Tall truck BB. You find these 366 and 427 TT in medium size trucks such as school buses, etc.
Le Mans Master
Joined: Oct 2000
Posts: 8,897
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From: Santa Ana CA
The simple answer (and certainly for Chevy) is that it is based on the bore spacing.
This runs across most brand lines too, expect perhaps Pontiac which used the same block from their small V8s (maybe 326) to their large V8s (maybe 455).
This runs across most brand lines too, expect perhaps Pontiac which used the same block from their small V8s (maybe 326) to their large V8s (maybe 455).
Team Owner
Joined: Oct 2004
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From: Springfield MO
St. Jude Donor '07
The 307 inhabits a very odd place in that it uses pistons that are identical to the SBC-based 250 I6 motor, but flat-topped instead of dished. You could probably run a stock 250 on 79 octane gas, the compression is so low. The 307 pistons help a LOT.
Le Mans Master
Joined: Dec 2006
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From: Oquirrh Mountains
St. Jude Donor '09
A BBC can be had in as large as 727 cid. Still lots bigger than the biggest sb.
Melting Slicks
Joined: Oct 2008
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From: Regina Sk Canada
The 307 dates back to the late 60s, and the 305 was used in F-bodies and the 1980 CA Vettes. Smog-era, maybe...but probably not Mexican.
The 307 inhabits a very odd place in that it uses pistons that are identical to the SBC-based 250 I6 motor, but flat-topped instead of dished. You could probably run a stock 250 on 79 octane gas, the compression is so low. The 307 pistons help a LOT.
The 307 inhabits a very odd place in that it uses pistons that are identical to the SBC-based 250 I6 motor, but flat-topped instead of dished. You could probably run a stock 250 on 79 octane gas, the compression is so low. The 307 pistons help a LOT.
