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400sb VS 396bb

K85 Octane

K85 Octane

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Really dumb question. I'm sure Google AI could answer but I'd rather start a conversation.

I'm curious what the differences between a 400sb and a 396bb would be. Physical size, weight, stroke, bore, bearings, cooling, valves, runners, etc etc.

Just a fun comparison. It "feels" like maybe the stroke and bore would be similar but since everything is larger around the rotating assembly you have major differences like what's above.

Same compression
Same cam values
Same carb
Why would one be better than the other outside of commercial HD applications?

Blah blah blah :D
 
Also, what type of heads being used ( on both SBC & BBC ) is a major factor on comparisons - there is so much more to it than just fairly common bore and stroke dimensions.
 
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Well that's just it. You won't find BB heads with the same valves and runners as most SB heads. That gives the BB an advantage, can't fit those valves in a SB.

But...big valves and runners are normally thought of as higher RPM power which isn't "normally" a BB trait. They tend to be lower compression work horses until "hobbyist" open them up.
 
K85 Octane said:
Well that's just it. You won't find BB heads with the same valves and runners as most SB heads. That gives the BB an advantage, can't fit those valves in a SB.

But...big valves and runners are normally thought of as higher RPM power which isn't "normally" a BB trait. They tend to be lower compression work horses until "hobbyist" open them up.
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There are several variations of runner volumes for each including BB ports that are in the normal SB territory - ya just gotta decide on which versions you want to make your comparisons off of.
But if you’re really getting down in the nitty gritty of things then you’ll need to consider rod lengths comparisons too for piston dwell effects on each combo.

Either setup can be made to make good power if the combination for all components involved compliment and plays well with each other.

For reliability and ease of potential power I would favor the big-block - excluding piston and stroke dimensions ( 396=4.094” x 3.76” ~ 400= 4.125” x 3.75” ) the ole say’n still holds true : “size matters” for ( as BENT mentioned ) bearing surfaces, girth of journals and block, rod length, pin sizing, potential runner volumes and valve sizes, plus the benefit of the canted valve angles of the big-block, etc.

If given the choice chances are a 396 BIG-BLOCK will not disappoint and power will come cheaper if using OEM parts selection - if aftermarket stuff is on the table then the skys the limit in both choices.
That being said I’d still go with a big block - just like I wrote on my book covers in middle school “Van Halen Rules !” the same holds true for big-blocks; “They Rule !” Just say’n.
 
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K85 Octane said:
Well that's just it. You won't find BB heads with the same valves and runners as most SB heads. That gives the BB an advantage, can't fit those valves in a SB.

But...big valves and runners are normally thought of as higher RPM power which isn't "normally" a BB trait. They tend to be lower compression work horses until "hobbyist" open them up.
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Well if you are interested I happen to have a good running bbc396 that was opened up to 402 in the c10 that I sold and he is putting an LS instead and I am buying it back from him.
It was also modified with a better cam for more power, not by me but the guy I got it from.
It has a barely noticeable lumpy idle
 
I've never owned a 396/402, but had a few 400s, and the last one was built and would pull like a freight train. I'd imagine the big block would pull just as hard if not harder. I'd say big block, there just cool.
 
Had a built 400 sbc years ago . . Sure do miss it :doah:

30 over / blue printed / weight matched everything / knife edge crank / polished everything / good 76cc heads . Not sure cam . She was a power house in my k30 on 4.10 gears and 38" swampers .

Guy who built it i found later . He had it in a 78 z28 for 1/4 mile drags and did crazy #'s with it . He told me swap a set of good 64cc heads back on and hold on even more . .

Sad i never got to . Spun a belt over heated and thinned the oil to much and boggered the #1 rod bearing up . .

She would show up a lot of people . . Buddy had a short bed on tons with 4.56 gears and all same but 454 edelbrock top end package . . . We raced 1 time and he got me out the hole on the strip but i walked him with the more rpms of the sbc 400 . .

They both have there place . . Depends on what you are going for .
 
I haven’t run either sized block in more than 12 years. However, I vividly remember everything about my 396 was much more expensive than a similar part on a small block. Small block consumables like valve cover gaskets, intake gaskets and such are probably in any auto parts store in the country. Big block stuff is rarely in stock was my experience.

Besides those things that do affect the ownership experience. If I was going to go gas again. I would go big block. The big block just seems so less stressed doing normal stuff while a similar powered small block it feels like it is being pushed harder.

Then there is the WOW factor when you open the hood and see those big fat valve covers. Just writing about it has me wanting a big block again.
 
I dig reading the stories!
BUT I'm not in the market for an engine. I have an engine, it's a 400.

My curiosity was the CI are similar but the ability is not.

Like say a 283 and a Ford 289. I would assume they are closer to the same VS the two engines from post #1.

BBC is, guessing, going to have every bearing bigger, valves, guides, springs, oil and water passages, pushrods, etc etc. All that makes for a robust engine, heavier, uses power to make power...= better?

Wondering what all the changes were. :D
 
Barrman said:
I haven’t run either sized block in more than 12 years. However, I vividly remember everything about my 396 was much more expensive than a similar part on a small block. Small block consumables like valve cover gaskets, intake gaskets and such are probably in any auto parts store in the country. Big block stuff is rarely in stock was my experience.

Besides those things that do affect the ownership experience. If I was going to go gas again. I would go big block. The big block just seems so less stressed doing normal stuff while a similar powered small block it feels like it is being pushed harder.

Then there is the WOW factor when you open the hood and see those big fat valve covers. Just writing about it has me wanting a big block again.
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I agree.
Everything I have now is either diesel or BBC
 
I went diesel mainly because of the fuel being able to sit in the tank more than a week or two on a vehicle that is not my daily driver.
 
K85 Octane said:
I dig reading the stories!
BUT I'm not in the market for an engine. I have an engine, it's a 400.

My curiosity was the CI are similar but the ability is not.

Like say a 283 and a Ford 289. I would assume they are closer to the same VS the two engines from post #1.

BBC is, guessing, going to have every bearing bigger, valves, guides, springs, oil and water passages, pushrods, etc etc. All that makes for a robust engine, heavier, uses power to make power...= better?

Wondering what all the changes were. :D
Click to expand...
As you mentioned - comparing a Chevy 283 to a Ford 289; the 289 would have a clear advantage in bore size at 4” v/s 3.875” so breathing would be greater and less valve shrouding if all else was equal induction wise.
 
Thats a huge difference in c.i. But I still think the 396bb would make peak tq lower than the 400sb, and more tq as well.
I had a head guy tell me a same size bb will break drivetrain parts more often than sb would.
 
The big block is going to put at least another 100 pounds over the front axle, maybe closer to 200, which is the only real disadvantage other than parts cost. The 400 SBC has a reputation for overheating and cracking. This is probably overstated, but the big block is able to flow more water and has more iron in those areas. Such durability does matter if we're talking about parts that were cast 50 years ago.

Barring a period-correct build or that you happen to have a good 396 on hand, I can't see why you'd pick one over a 454, though. They are way more common, would be maybe half as old as a 396 and give you more power and torque at the same size and weight. I suppose that's obvious, but just not the point of this thread.
 
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