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What changes between a small block and a big block

This is a discussion on What changes between a small block and a big block within the Internal Engine forums, part of the LSx Technical Help Section category; Or, whats the difference? I know the lt1, ls1 etc are "small block" but i've also heard of a 400 ...

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    What changes between a small block and a big block

    Or, whats the difference? I know the lt1, ls1 etc are "small block" but i've also heard of a 400 small and 400 big block, and obviously the 8100 truck engine was a big deal cause it was the "last production big block" i know its a rookie question but figured i'd learn from the best..

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    You aren't comparing apples to apples. They are different lines of engines. There is no LS big block. Factory displacements are from 4.8 to 6.0 liters. After market LS tall decks are getting montrous (over 450 cubic inches, sorry I don't know the metric equivalent off the top of my head) The LS series engines are considered Gen III on up. Gen I started in 50's on up until fairly recently. Gen II was the LT engine which was kind of it's own lineage with reverse water flow.

    Big blocks went by Mark "X" series engines. I don't remember how high the designation went. I think the last series is Mark VI. I believe the Mark series engines are still available in commercial vehicles and RV's but not in regular trucks.

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    cool, good info...I know theres no LSx "big block" im talkin more widespread, generic "difference between small and big block engines" is it literally just the size of the block? and how so?

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    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by ls1fan74 View Post
    cool, good info...I know theres no LSx "big block" im talkin more widespread, generic "difference between small and big block engines" is it literally just the size of the block? and how so?
    Yes the blocks and cylinder heads are physically different in size and shape. I'd send a picture of both from my own vehicles but I don't see the little linky thing at the bottom of the screen anymore to post pics.

    Put simply,,,you can't mistake one for the other.

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    The block is obviously larger... and so are the internal components... The displacement is also a higher number some of the time.

    Stock GM disp. numbers included, but weren't limited to:

    SBC:
    262, 283, 302, 305, 327, 350, and 400

    BBC:
    366 (commonly found in big trucks and busses), 396, 402, 409, 427, and 454...

    A major way to tell the difference in a quick glance is the exhaust ports....

    SBC:
    O___OO___O


    BBC:
    O__O__O__O
    Last edited by FORD RECOVERY EXPERT; 07-09-2009 at 09:26 PM.

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    Yes notice how the BBC exhaust ports look just like LS engines???

    Also if you look at a pair of LS3 cylinder heads with their large square ports,,,they were new to the LS series engines but are surprisingly similar to the old BBC square port heads.

    Some of this technology is nothing new,,,it's just being reapplied to new platforms. Pretty cool.

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    ah good call with the exhaust ports, I didnt realize that before....now I do! what would be the purpose of big vs small, being able to handle more torque? Like why use a BB 366 in a bus/work truck vs. a SB 400?

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    bore spacing .sbc 4.4 ,bbc4.84.in the old days they over built things with alot of cast iron for durability.

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    BIG block- a lot of wieght, torque and looks.

    small block- light (especially LSX aluminum) Small, And can wind out close to same power at high rpms.

    to get a big block to spin will cost and I would even bet to say it would cost the same or more than building the hell out of an LS motor.

    Also Big blocks are large displacement and I don't care how conservitive you build one, it will always suck fuel.

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    Quote Originally Posted by JaycenK View Post
    BIG block- a lot of wieght, torque and looks.

    small block- light (especially LSX aluminum) Small, And can wind out close to same power at high rpms.

    to get a big block to spin will cost and I would even bet to say it would cost the same or more than building the hell out of an LS motor.

    Also Big blocks are large displacement and I don't care how conservitive you build one, it will always suck fuel.
    thats basically what I thought....so they're about high torque, "stump-pulling" applications mostly, and it costs a lot to get a BB to race car specs. I see. so why is the horsepower in the vortec 8100 so close to the 6.0L LQ4 in say a sierra 2500HD? the six liter made 300/345 i think and the 8.1 made 350/450 torque is obviously the difference, but why would you pick one over the other?

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    Quote Originally Posted by ls1fan74 View Post
    thats basically what I thought....so they're about high torque, "stump-pulling" applications mostly, and it costs a lot to get a BB to race car specs. I see. so why is the horsepower in the vortec 8100 so close to the 6.0L LQ4 in say a sierra 2500HD? the six liter made 300/345 i think and the 8.1 made 350/450 torque is obviously the difference, but why would you pick one over the other?
    exactly like you said torque....for pulling/towing operations..a big block will pwn ..for a race high hp a small block..now obviously there are exceptions...size constraints and weight are other obvious ones

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    Quote Originally Posted by shady milkman View Post
    exactly like you said torque....for pulling/towing operations..a big block will pwn ..for a race high hp a small block..now obviously there are exceptions...size constraints and weight are other obvious ones
    does anyone use that 496 vortec as a high HP motor, or is that retarded? btw I just saw your avatar pic thats hilarious

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    First let me clearify some things.

    As far as fuel economy,,,if thats what you are into then it's time to change hobbies.
    If you build a small block for big power numbers it's not going to suck any less fuel than a big block. That's just a common stereo type. I get mileage figures out of my bigblocks that rival any well build small block, because I have some of those too.

    Big blocks will and can spin rpm just fine without high dollar internals. I have had factory bigblocks that turn 65-7000 rpm right off the bat.
    Those that think big blocks can't spin haven't driven a 396/375 hp or a 427/425 hp big block before. I've owned and/or driven both and I can attest to their high rpm capability in stock form.

    Now in the days of small blocks being limited in displacement,,,most people would go for a big block for their broad torque curves, better cylinder heads, and the potential to make more power with more cubic inch.
    In todays market,,,although bigblocks still have a huge appeal,,,,you can build large cubic inch small blocks that have broad torque curves and make great hp with all the good aftermarket cylinder heads on the market now,,,,and keep it in a small package.
    On the same token,,,,you can now build huge cubic inches from a bigblock now that can't be done on the smaller platform of the small blocks.
    They have both grown leaps and bounds.

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    im sure some do..but for our cars and most cars..the sbc are what they use...the number are attainable and fitment is not such a issue

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    Quote Originally Posted by shady milkman View Post
    im sure some do..but for our cars and most cars..the sbc are what they use...the number are attainable and fitment is not such a issue
    I'm a little lost on you meaning??

    For a real comparison we have to go back 40 years when big blocks were being used in passenger car applications.
    They haven't been put into passenger cars since the mid 70's,,,,and by the late 70's and into the 80's you could only get bigblocks in truck type applications.

    With that said,,,cars since the 80's just weren't engineered with bigblocks in mind anymore,,,,,,,although swaps are done regularly,,,fitment isn't easy because of the simple fact that GM didn't mass produce the cars with that in mind.
    Before this time when bigblocks were actually offered in anything from camaros and novas up to station wagons,,,,a big block swap is a walk in the park, and can be done with factory engineered parts.

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    Quote Originally Posted by ls1fan74 View Post
    does anyone use that 496 vortec as a high HP motor, or is that retarded? btw I just saw your avatar pic thats hilarious
    Quote Originally Posted by shady milkman View Post
    im sure some do..but for our cars and most cars..the sbc are what they use...the number are attainable and fitment is not such a issue
    Quote Originally Posted by Firebirdjones View Post
    I'm a little lost on you meaning??

    For a real comparison we have to go back 40 years when big blocks were being used in passenger car applications.
    They haven't been put into passenger cars since the mid 70's,,,,and by the late 70's and into the 80's you could only get bigblocks in truck type applications.

    With that said,,,cars since the 80's just weren't engineered with bigblocks in mind anymore,,,,,,,although swaps are done regularly,,,fitment isn't easy because of the simple fact that GM didn't mass produce the cars with that in mind.
    Before this time when bigblocks were actually offered in anything from camaros and novas up to station wagons,,,,a big block swap is a walk in the park, and can be done with factory engineered parts.
    im sorry i missed the quote..it was in reference to ls1fan's question about the 496

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    good info, thx guys- i kinda wanna find an old project car with a big block to mess around with

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    Quote Originally Posted by FORD RECOVERY EXPERT View Post
    The block is obviously larger... and so are the internal components... The displacement is also a higher number some of the time.

    Stock GM disp. numbers included, but weren't limited to:

    SBC:
    262, 283, 302, 305, 327, 350, and 400

    BBC:
    366 (commonly found in big trucks and busses), 396, 402, 409, 427, and 454...

    A major way to tell the difference in a quick glance is the exhaust ports....

    SBC:
    O___OO___O


    BBC:
    O__O__O__O
    Great info and glad someone remembers that the 366 is a BB.
    Built one of these bastards right before i graduated. Guy spent all kinds of money on the rebuild and I did the detail work, but didnt want to rebuild the carb/buy a new one.


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    BB can spin. Ive spun a 454 with very, very mild internals past 7000 on a engine dyno. Many back to back runs.

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    Quote Originally Posted by azfrc View Post
    ... There is no LS big block. Factory displacements are from 4.8 to 6.0 liters. ...
    You forgot the LS7 - 7.0 liters. Isn't the LS3 6.3 liters?

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