What constitutes a "small block" engine?
Team Owner
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St. Jude Donor '07
Melting Slicks
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From: Lehigh county Pennsylvania
I will. It and its predecessor the 348 were the 'W' series engines from the configuration of the valve covers. Many found their way into medium sized trucks. Not a 'small block' in any respect. They evolved into the Mark II big block with their "porcupine" valve arrangement.
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St. Jude Donor '14
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I guess the best way to say it every SBC that has ever been put between the frame rails from the factory production line has been a 4.44 bore center. Every form of BBC including the W engines uses a 4.84 bore center.
You get two flavors of aftermarket SBC with 4.44 or 4.50 bore center.
BBC aftermarket are 4.84, 4.90, 5.00 are common sizes. I did see a 5.30 bore center.
632cu. are built off 4.84 bore center the others can go well north of 800 cu.
NHRA Pro stock rules 500 engines use a 4.90 bore center limit. 4.730 bore 3.50 stroke real short deck for that 3.50 stroke.
You get two flavors of aftermarket SBC with 4.44 or 4.50 bore center.
BBC aftermarket are 4.84, 4.90, 5.00 are common sizes. I did see a 5.30 bore center.
632cu. are built off 4.84 bore center the others can go well north of 800 cu.
NHRA Pro stock rules 500 engines use a 4.90 bore center limit. 4.730 bore 3.50 stroke real short deck for that 3.50 stroke.
Last edited by Little Mouse; May 29, 2012 at 12:16 PM.
Melting Slicks
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Le Mans Master
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From: Seattle WA
St. Jude Donor '14
So, what constitutes a small block engine?
...and there are (currently) 4 generations
I agree that at least at the moment, the common bore spacing will do it. But maybe the only answer is that a small block is whatever GM calls a small block
Intermediate
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From: Austin Texas
With 400's wasn't there a "TurboJet" and a "TurboFire". If I recall correctly the TurboJet was the 402 marketed as a 400 in intermediate (Non SS Chevelle) and Large Cars (Impala) etc.
TurboFire was the small block siamesed 400.
...of course I may have those names reversed.
TurboFire was the small block siamesed 400.
...of course I may have those names reversed.
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Team Owner
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St. Jude Donor '07
I still have to vote that general engine size is what determines a "small block" vs. "big block." BBC blocks are...well...bigger.
Le Mans Master
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St. Jude Donor '14
There are two families, and multiple generations within them - just that simple.
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Le Mans Master
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Its the very big difference in bore spacing. You can stroke a gen 1 or an LS or LXS out to the size cu. of the old BBC but its still just a pumped up in displacement small engine. The BBC is the real thing a big engine.
Your stuck with the small bore centers on a SBC.
Your stuck with the small bore centers on a SBC.
Safety Car
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From: Seattle Washington
My 2 cents worth. Despite GM's marketing dept decideing that it would be good for there image to call the LS Engine a SBC I don't consider it one, and never have. Its not that I don't like it, I own one its got 94k trouble free miles on it. But some times its better to let something die. One thing I have never read or herd about was why GM decided when to replace the SBC. I mean they couldn't be the last company producing a non metric engine. A more modern engine must use a more modern manufacturing process and therefore cost less, the cylinder head on the SBC had run its coarse on performance and emissions. And many more reasons. But why 1997 ? Did they feel they had to launch it with a new model Corvette? After all the Corvette has always been the test bench for new Idea's for GM but was that it? Dose anybody know when the SBC was last sold in a Vehicle? I think there were some 2000 trucks sold with them. So if the SBC was from 1955 to 2000, then the BBC has had a longer run than the SBC, 1965 to present and still counting as far as I know. Who ever said engines needed to be metric anyway.
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My 2 cents worth. Despite GM's marketing dept decideing that it would be good for there image to call the LS Engine a SBC I don't consider it one, and never have. Its not that I don't like it, I own one its got 94k trouble free miles on it. But some times its better to let something die. One thing I have never read or herd about was why GM decided when to replace the SBC. I mean they couldn't be the last company producing a non metric engine. A more modern engine must use a more modern manufacturing process and therefore cost less, the cylinder head on the SBC had run its coarse on performance and emissions. And many more reasons. But why 1997 ? Did they feel they had to launch it with a new model Corvette? After all the Corvette has always been the test bench for new Idea's for GM but was that it? Dose anybody know when the SBC was last sold in a Vehicle? I think there were some 2000 trucks sold with them. So if the SBC was from 1955 to 2000, then the BBC has had a longer run than the SBC, 1965 to present and still counting as far as I know. Who ever said engines needed to be metric anyway.
The LS has the same 4.40 bore center as the SBC it replaced the deck did go from 9.025 to 9.20. But both these figures are tiney compaired to the factory BBC 4.84 bore center, 9.80 deck height.
It for sure is SBC based.
The most disapointing thing to me was when i first read about the new SBC was they kept the 4.40 bore center.
All the nice changes and they kept the same stupid 265 chevy bore center.
Last edited by Little Mouse; May 30, 2012 at 12:59 PM.
Team Owner
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With all the information above, I never spotted the switch in the mid 80's to the roller cam and single piece rear main seal on the SBC, by '88 I think it was across the line, for instance I have a '89 factory 4 bolt main cap 355/.030 over roller engine in my car, since '97 now....various heads...iron, aftermarket aluminum, and now L98 stock aluminum, L98 cam now, after getting burnt for YEARS with a defective roller cam from TPIS, never buy a ZZ9 cam from them or anything else for that matter....long story...the ROLLER cam was junk from the git go, and I never suspected....
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Team Owner
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From: Springfield MO
St. Jude Donor '07
I didn't say "displacement," I said "size." Physical size. Every US manufacturer has small and big block engines. Small blocks are smaller than big blocks. End of story.