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Tuned
Joined: Dec 2012
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From: Fouke, Arkansas
Back to Basics
Can anyone help me understand the difference between a big block and a small block? Is there any way to pop the hood and simply look at an engine and know if it's a big or small block? This has always confused me and any help would be greatly appreciated. Thank you in advance for sharing your knowledge.
Cargo Master
Joined: Apr 2003
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From: Parkesburg PA
It started because some blocks were bigger then others. Then it sort of became linked to displacement. For example the Pontiac 350 and 455 have the same sized block externally but the 350 is considered a small block and the 455 is a big block. The displacement is around 400ci where smaller is a small block and larger is a big block but it's a grey area.
When you pop the hood you can tell once you learn to recognize the different motors. A 302 or 351 would be a small block. The 460 is a big block. The 400 may be considered a big block because of the displacement but it can also be a small block. So people just call it a 400...
When you pop the hood you can tell once you learn to recognize the different motors. A 302 or 351 would be a small block. The 460 is a big block. The 400 may be considered a big block because of the displacement but it can also be a small block. So people just call it a 400...
Cargo Master
Joined: Apr 2003
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From: Parkesburg PA
Since the small/big block description started in the 50's/60's we'll look at the classic Small Block Chevy vs Big Block Chevy. Next we'll compare a 5.0 ford and a 4.6 DOHC... You'll notice the 4.6 is much larger... So you can see the distinction is now clear as mud...
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another way to tell is valve covers and the intake. fords 351w intake is slightly larger then a 302 but a 390 fe motor, 428/429 and 460 have significantly larger intakes and valve covers. also the over all length from the left head to the right head will be larger on a 460 then say a 302 351 even a 400(351m)
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Tuned
Joined: Dec 2012
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From: Fouke, Arkansas
LOL yes it is clear as mud now. I do have a little better understanding now but I suppose I'm the type who likes to call it like it is. A 351 is a 351 and a 460 is a 460, that's easier for me to understand that someone saying "that's a big block" or "a small block". IDK it's just what makes sense to me personally. Thank you gentlemen, I appreciate you sharing your knowledge.
Cargo Master
Joined: Apr 2003
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From: Parkesburg PA
Some engines, typically the classic ones, are referred to as big/small blocks because it was clear by looking at them (see the Chevy pic above). That includes the 351 and 460. The 5.4L is bigger than the 4.6L but I don't think I've ever heard anyone call the 5.4L a big block.
It's vague and something that you just sort of assimilate over time that some engines have, well, a nickname of being a big or small block. So if someone asks you "Hey, do you have a small block in that truck?" You could answer "Yes, it's a 351". Or, "No, it's a 460 - I love the big block power it has..."
In my best Ron Popeil voice - But wait! There's more!
Chevy's small block is referred to as a mouse motor and the big block is a rat motor. Despite trying to figure it out, no one really knows the origin or which one came first. Also, it seems to only apply to the classic small block / big block Chevy.
There are ton's of nicknames for motors - cammer's, mod motors, windsors, etc.
It's vague and something that you just sort of assimilate over time that some engines have, well, a nickname of being a big or small block. So if someone asks you "Hey, do you have a small block in that truck?" You could answer "Yes, it's a 351". Or, "No, it's a 460 - I love the big block power it has..."
In my best Ron Popeil voice - But wait! There's more!
Chevy's small block is referred to as a mouse motor and the big block is a rat motor. Despite trying to figure it out, no one really knows the origin or which one came first. Also, it seems to only apply to the classic small block / big block Chevy.
There are ton's of nicknames for motors - cammer's, mod motors, windsors, etc.
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Basically from my experiences NORMALLY, I stress that again, normally anything 400 ci or smaller is a small block where anything 401 ci or larger is a big block. But that statement doesn't apply to race scenerios that's a whole nother animal
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Tuned
Joined: Dec 2012
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From: Fouke, Arkansas
Thank you gentlemen, honestly it is a little clearer now. If I understand correctly the term "big block" literally refers to the physical size of the block and not really the horsepower or CID. No doubt racing is a completely different ball game. There does seem to be some "gray area" when referring to a big or small block in relation to say the 351 CID engines. Again I thank you gentlemen for sharing your knowledge.
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Cargo Master
Joined: Apr 2003
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From: Parkesburg PA
If I understand correctly the term "big block" literally refers to the physical size of the block and not really the horsepower or CID.
The 400ci crossover is a good generalization however there are exceptions. I'll go back to the small/big block chevys because it's such a clear example and they used the same two engine families for 30+ years. The small blocks went from 262ci to 400ci in factory form. The big blocks went from 396 to 502ci. So you could have a 396ci big block and a 400ci small block.
With the aftermarket it's possible to have 450+ci small blocks and 700+ci big blocks... Similarly equipped and sized the big blocks will usually have more power due to their cylinder heads. Big blocks typically came with big heads that featured splayed valves - were they're angled for better flow as opposed to being in a straight line like most small blocks. The 351m, Cleveland, boss and 400 motors are small blocks that have splayed valves. Big blocks, especially truck big blocks, are typically associated with low end grunt.
Then of course you have the FE's which are considered a medium block...
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Tuned
Joined: Dec 2012
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From: Fouke, Arkansas
Thank you beatertruck, I really appreciate you sharing your knowledge with me. Honestly I can't say it is 100% clear but I can say I am a heck of a lot more knowledgable about this than I was. Thank you for your input gentlemen.
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