If you had to build one or the other for performance reasons, which one would you do? Why or why not?

What is the exact usage? Your post is way to general.

Well, lets say street/strip use. Oh, and I'm not counting originality either.

I'm partial to big blocks, cubes is the way to go....... :D

396/402, BB's have much better breathing heads. More than make up for the weight. Both engine have nearly the same bore (4.125 vs 4.096/4.125) and stroke (3.75 vs 3.76) but the BB has longer rods. Which provide a better R/S ratio and less side loading on the cylinder wall. In some testing that a mag did comparing the two, the BB came out ahead.

Originally posted by texastornado:
...cubes is the way to go....... :D In this comparison, the SB wins by 4 inches smile.gif .

One problem the big block has besides overall weight is heavier reciprocating weight. That crank is a monster.

After comparing and contrasting the two it almost seemed as if it would be worth more to do a 400 sbc as compared to a 396 bbc. The 400 is lighter, the bore is bigger and parts are probably more readily avaliable.

But now won't a pair of aftermarket heads (AFR, Dart, etc) for a small block help a 400 flow just as well if not better than a big block?

the crank and heads are both monsters,,,but I'll take em anyday.

There was a magazine not too long ago about 406 small block versus 408 big block. They spent 2,500 on the small and 3,500 on the big, and they put both into a 1st gen Camaro. Both ran low 12's, the big block won by a few tenths.

The small block was cheaper, and much easier to work on, and maintenance is easier in terms of small parts costs. It is also easier to shoehorn a small block into a car.

If it were me, I would rather just savethe money and go small block.

If I were to go big block, I would go all the way with a 468 or 496. A 396 just really isn't worth it IMHO, unless it was in a Nova :D

If you are going to put a lot of miles on the car use a BB. The 400SB has a bad habit of not living for very long when stressed unless you go to an aftermarket block.

I think you've got that backwards...have to spend more on a smallblock so it can run with a big block. Smallblock parts are cheap,but the good heads aint. ;)

Originally posted by gasgzlr:
If I were to go big block, I would go all the way with a 468 or 496. A 396 just really isn't worth it IMHO, unless it was in a Nova :D That's exactly what I was thinking.....if I do a big block I wouldn't waste my time on a 396 and opt for at least a 454 instead. That would be like me wanting to play with a 305 when a 350 would take me a longer way.

Right now I'm trying to decide if I want to go with a 400 sbc in my Chevelle as it's already currently set up for a small block......or if I want to go to a 454 but then I'm gonna be swapping the trans. as well.

I have an article in Chevy high performance where some kid with a 406/TH350 and a 4.10 rear in his '70 Chevelle is running 11's n/a and a pair of MT ET streets so that's what's got me convinced I can do it too.

Oh....where can you get aftermarket 400 blocks?

Right. It's like building a 283 when a 350 would just be more power.

Aftermarket 400 bore/mains blocks: Dart Little M, World MoTown blocks. 1500-1800.

both are great engines. big block looks better. both work great

i personally would take the small block, no doubt. Generally the big block will always make more top end horsepower with the larger volume/flowing heads, and higher lift camshafts. However, the SB should make more low end torque (not always more peak torque) with the smaller volume heads. I've done several engine simulations that back up the theory, but no real life proven results. As for price, to upgrade both on a level playing level the big block will always cost more. After market BB heads = $$$. After looking the hp/tq of both engines and I'd be happy with either, the weight is one of the biggest deciding factors for me. Lower weight is faster, easier on parts, better braking and handling too. In terms of performance only, i will take low weight over power. I personally wouldnt bother with a big block less than 427 ci. But thats me. But of course it all depends on what parts are in each engine to make a real good comparrison.

Big blocks don't need aftermarket heads...its the smallblocks that need them to keep up with the big block. A smallblock will not make more torque down low either graemlins/thumbsup.gif

Bob,
Actually a 408 SBC will make more torque at low rpm than a 408 BBC under similar conditions.
The smaller intake runner and valves create more velocity at low rpm and make slightly more torque.
Usually at less than 3000 rpm, and it doesn't matter because on the track the car never sees this rpm range. The difference is also pretty small. More than made up for by the flow capacity of the BBC heads/valves.

Even a large runner aftermarket 23 degree SBC head is needed to compete with an slightly worked BBC OEM oval...

So the BBC can actually be built cheaper. No need for aftermarket heads, sometimes not even larger valves.

The CHP article a few years ago was trying to make the comparison as fair and equitable as possible and they did a decent job. I think it was only 3 tenths difference in the same car...

However they put oval Merlins on the BBC, and the equiv. SBC head on the small block. Sportsmans?

Anyway,
They could have saved the money on the Merlins and just installed bigger valves in the stock 396 heads... andon the 408 cube probably could have done as well with the stock 2.06/1.72 396 valves given a proper radiused valve job and backcut valves..

Then the money comparison would have been almost the same, the BBC still would have won ET wise, and it will ALWAYS look better under the hood smile.gif

396 all the way for me been building them and other bbc for about 13 years now........and with my buddys who race they are allways seemly putting in more money into there sbc to keep up with my stock bbc parts............

stock bbc heads are easy to get into the 10's even with the back yarding port work and putting in the 2.19 /1.88 valves.......so thats pretty cheap.......stock cranks and bottom ends will live for years.......so you really only need to buy the pistons........ and then pick you favorite cam...........intake can be had for well under 100 bucks(used) and you can slap any 750 or bigger holley on there........match the convertor and gears and with any decent cam and intake 11 are so easy to run into with even with the 396............so there really is not a big budget for bbc.........its just those who dont build them think there is........you dont have to go out and buy new everything for a bbc unless you looking for deep deep sub 10 sec range...........

Won"t a big block make more low end tourqe than a SB because of the weight of the rotating assembly?

Bad Rat,
The weight of the rotating assembly doesn't "produce" torque. So no it will not make more torque on the bottom end on an engine dynamometer.

It takes more power to accelerate the weight, and more power to decelerate it too though...

So there would be an inertia effect, like having a heavy flywheel. Not a bad thing for launching a heavy car. But can also be just as detrimental..

The difference ET wise in the weight of the rotating assembly woul dbe immeasurable IMO.

Even though a BBC crank is 70+ lbs and the SBC is ~45 lbs, the motor doesn't necessarily "see" the difference in the weights. Not all of it anyway.
Since some of that weight mass is in the center of the crank, on the mainline, it isn't like having a heavy bobweight, it is spinning but not working against the motor...
BBC mains are .300 bigger than a 350 SBC crank, .100 bigger than a 400 main.
The rods are .100 bigger... So alot of the bBC ranks additional weight is in the center of the crank.

Of course some of it is in the counterweight to offset the heavier pistons/rods...

that magazine 400 was one sick puppy! they built a more mild motor than that later on with vortec heads and it made like 75hp more than that one. i will take a 400sbc anyday over a 402! if you're going to build a big block that IS NOT for originality, always start with at least a 454 block! ;) leave the 396/402's for the restorers and purists. graemlins/thumbsup.gif

Originally posted by Rapid Robert:
I think you've got that backwards...have to spend more on a smallblock so it can run with a big block. Smallblock parts are cheap,but the good heads aint. ;) I like small blocks but agree with this statement. A low cost 396 with a properly matched combo will make more power and last longer than a budget SB400. IMO. The 396 will require more stall than the 400. Just pay close attention to the compression on a 396, you need a pretty big dome to get 10:1 even with closed chambered heads.

A lot of 396's are slugs, probably because they have 8.5:1 and a .600 lift cam.

As far as that stupid magazine article... The ET's they gave were simulated by a program because they didn't have time. Then why did they show pics of the cars racing at a drag strip? Just like the cars in mags that hit "mid 11's" that have 12.80 on the window. Then there is King Rat...

Lonnie

I built the 396 because it was what I had as a running engine. If I had to start from nothing
a 454 or bigger would cost about the same as the 396. I agree with many here who have said a 406 SBC can give the same performance. I actually built a 383 for my brother that runs very close to my 396. That motor can be built rather inexpensively. If you are going to carry the weight of a big block it might as well be a big one.
All in all I'm pleased with the performance of my Iron headed baby Big block.

Sometimes the signature shows up sometimes not?
Anyway the Baby Bigblock has run 11.92 at 114 in my 3880# chevelle with a 700r4 and 2400 converter.

I tend to believe that Chevrolet would never have built the Big Block, if a small block could've done the job.

I read the article in Chevy High Performance, the price of the big block wasn't much more, and it out ran the small block, by about half a second, in a 2nd generation Camaro.

Both had the same compression, similar cam specs, and around 408 cubic inches.

Some people wrote in complaining about the big block having a better rod to stroke ratio, and better flowing heads, blaming those as the reasons the big block won.

I've been in some pretty hot small block cars, but I still think, it’s really hard to beat a big block when it comes to thrill producing acceleration.

I've run both a 406 sbc as well as a 414 bbc. You have to compare apples to apples.

Here is one major FACT that cannot be disputed. No FACTORY sbc head casting can compare with a factory bbc head. The ONLY way a 400 sbc can compete with a bbc is with aftermarket heads, but then you lose a true and fair comparison.

Secondly, a bbc can easily (even a 396/402) make 600+ hp with a stock block and factory casting heads with larger valves and some real mild cleanup work. For a 400 sbc to get to 600" hp, it NEEDS aftermarket heads as well as serious upgrades to the stock block. Factory 400 sbc 2 botl blocks are fine (with ARP studs) to approx. 550HP but any more and you need splayed caps. Also, 400 sbc's have a tendancy to crack blocks at the steam holes when pushed real hard. Then your talking an aftermarket block in addition to aftermarket heads.

Both engine combinations have their good and bad points. You also have to consider the performance level at which your considering.

I myself would not put good money into a 396/402 when a 454 core cost so little more and you have a much more potential for power while spending the same $$$ for internals and machine work.

The weight difference and cost difference are insignificant IMO.

And for not much more money you can make a 496 if the 454 has a bad crank in it..

AND 550 hp can be made easy!!

pdq67

Originally posted by 10secBu:
I've run both a 406 sbc as well as a 414 bbc. You have to compare apples to apples.

Here is one major FACT that cannot be disputed. No FACTORY sbc head casting can compare with a factory bbc head. The ONLY way a 400 sbc can compete with a bbc is with aftermarket heads, but then you lose a true and fair comparison.

Secondly, a bbc can easily (even a 396/402) make 600+ hp with a stock block and factory casting heads with larger valves and some real mild cleanup work. For a 400 sbc to get to 600" hp, it NEEDS aftermarket heads as well as serious upgrades to the stock block. Factory 400 sbc 2 botl blocks are fine (with ARP studs) to approx. 550HP but any more and you need splayed caps. Also, 400 sbc's have a tendancy to crack blocks at the steam holes when pushed real hard. Then your talking an aftermarket block in addition to aftermarket heads.

Both engine combinations have their good and bad points. You also have to consider the performance level at which your considering.

I myself would not put good money into a 396/402 when a 454 core cost so little more and you have a much more potential for power while spending the same $$$ for internals and machine work.

The weight difference and cost difference are insignificant IMO. i agree with Todd for the most part. for a street car i would always pick a 400sbc, if it was all out race but i had to use stock heads, definately a 396/402. the Vortec headed 400 CHP built made more torque and hp than the 402 in the shootout issue. i can't explain what was wrong with that 408 in the shootout issue, but if mid 12's was all that it ran in that Camaro then something HAD to be wrong. i've got almost the same setup in my 71 with the exception of Pro 1 cylinder heads and i GUARANTEE you i would smack that 408bbc all over the track even at 200lbs heavier than that Camaro. shoot, i'll even put 500lbs of ballast in the trunk and still smack it around. neither motor was very impressive, IMO, but that small block was just plain sick for what it had. ran more like a 350 than a 400, IMO.