whats your opinion on this 1.whats the difference between the 402 big block and the 400 small block as far as power and tq ratings.and also which would u guys prefer????  

dude...cubes are cubes..and so are pounds....BBC = VEry heavy
SBC = lighter....

Go with the small block...parts are cheaper and they weigh less and all that jazz
The 396/402 are the "305" of the big block family....sure they can make power...but why not just get a 454...they made more of em....easy cubes....but still 400 cubes is alot from a small block and even that can be massaged into more...say 421

This is going to start an argument...butI dont care
small blocks are better pound for pound than a big block any day...IMHO.

-Shred

No argument here.

Bogie

I know, old topic but I have to argue that!! OK, so you say cubes are cubes!! I guaranty you that a big block 402 with stock heads and decent cam say .560" and around 238* at .050 would put out way more torque which then means more HP!! A set of large oval port stock BB castings with right valves and bowl work will out flow a high performance set of small block heads!! Thats that! Ya i know some really high dollar keith dorton heads from trickflow makes gobs of power, but lets be real, you average street guy cant afford that!! I dang sure cant!  Small blocks ya, there light.. but considering most of your horse power comes from your heads, lets see.. Example A, small block chevy head, a really high performance set, with 220cc intake runners, if you really dig deep you get 2.05" intake valve..dont know any flow numbers infront of me and i dont want to provide no kind of false information so here is the big block outlook: I have on my 427, 1967 Casting number 215, intake port is 255 cc, exahaust 118, and stock valve was 2.06, now has 2.19" intake valves, so you do the math then get back with me!! LOL i now i may sound like i think i know it all!! I DONT! ! But i do know the numbers never lie!!

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granted, the canted valve design of the bbc heads does offer its flow advantages... however the "thats , that. " portion isn't quite as "that" as you may believe. comparisons of flow curtain vs. flow dynamics... and hoestly, 402inches from a bbc is giving up a ton to 400 inches from a sbc. both share the ball park 4,125 bore , both share the ballpark 3.75 inch stroke. advatage to the bbc being the longer rod /stroke ratio, (which is hardly compensation for the weight penalty the bbc faces). and in terms of absolute airflow, yes the bbc will NEARLY always flow more air. but for a moment consider this, quality ,i.e. cyl. fill. is far more efficent means of making power than quantity. milestones such as the fast burn chamber,quench studies, ect... have brought the sbc a long way. the mark iv bbc and advancements in design are little more than at a standstill and have been for many years now. true. 2.05's on a mouse is a good compromise for a mouse making a little "warmed over" power, and is usuable in a 400 inch engine. overkill in this sensitive area sacrifices torque, drivabilty, cyl. fill, and overall power out put. one of my recent mouse buildups used sportsman 2 iron 200 cc runner heads that i worked for a 2.10 intake and rolled the short side in to take advatage of the mod. this however was a 421 inch mouse and would absolutely slam the tires/rear chassis w/ gobs of torque. earlier i mentioned flow curtain, if you are unaware it is the dia. of the valve  x's 3.14 (pi) x's lift of valve off of its seat. the 2.19 possible in a bbc head offers great advatages in applications where the larger valve can be used, a 2.19 inch intake without the corresponding short turn work in such a little 402 rat engine is useless. it may have cost 40 lbs.ft. especially if this is a dual plane, vac. sec., auto car with 3.55's (or worse) besides the engine alone gives up  150 lbs.+ to its little bro.

yes bbc do rule. use your mods wisely , race responsibly, and if you mod for bench race cred, throw n2o at it. looks good people know it rocks and you never have to use it. your stock motor response and drivability are there at your foot. your cool points are at the cruise in when you raise the hood.

 yes i do love sbc's. i have many. yes i do love bbc's . i have many.

 and pontiac, and caddy 500's, i do keep an open mind. i have hundreds of builds to my credit and thousands of hours at the dyno. i offer my advice to get you the most by detouring you around the pitfalls i have witnessed in these situations whether they were my own or the company i worked for.  anything i can do to help good luck.

 quick tip to the small blockers outthere, longer rods fool your heads into thinking they are better for the app. get with a knowledgeale tuner prior to shelling out bigtime dough to your local "porter" .heads make or break the combo. i have found that there are far more "ricky rev's" out there than actual porters.

Hey guy's thanks for the response i know the topics are old but hey who cares theres somebody out there that needed that info you offered so once again thaanks!!  

All really depends on what you want to use the engines for. Theoretically, the 402 could be built to out power a 400 simply by virtue of big block heads having port and valve sizes far larger than what can be obtained from small block heads. So if you picked some astronomical RPM above what an SBC head can feed, then the BBC will out power it.

If you're building something more down to earth like a truck for towing, you might find that a BBC will require peanut port heads to run decently in the needed RPM range. This is because as the ports and valves get bigger, against any RPM, the comparative air flow speed becomes slower. This reaches a point where a carbureted or TBIed engine can't keep fuel in suspension and the low speed flow lacks the ability to feed the engine during overlap so bottom end torque sags. The solution is either smaller ports or stiffer gears which get the revs up. Either solution speeds up mixture flow bringing low to mid range RPM torque up. The exhaust suffers the same problem in the same RPM ranges so the exhaust stalls out in the ports and manifold and doesn't help blow down as the piston approaches TDC, this leaves the combustion chamber volume full of exhaust gases after the end of the exhaust cycle.

Frankly, except for building really big blocks like 427 or bigger, I've never really seen the advantage of BBC heads on a smaller displacement engine, unless you can keep it above 7000 RPM. In my opinion canted valves are highly overrated as offering any real assistance to air flow, at least as the BBC intakes are laid out. It's an old problem, for a center mounted carbureted configuration 4 of the intakes naturally aid induction and swirl and 4 don't. With the exception of SBC 2.2 Mirror Port heads and Oldsmobile production heads, it seems nobody at GM, Ford, or Chrysler has figured this out. I sometimes find myself wondering if there's any advantage to chasing Coanda effects on the short side turn to the valve. When one looks at the power obtained by the Gurney-Westlake Ford 302 heads against the SBC 302 with conventional Chevy heads, the theoretical power gain of high port angle, and canted low angle, large diameter valves just isn't there. I mean it's there but the effect isn't as significant as modelling predicts. Remember about this time Chevy had built SBC Hemi heads and scrapped the whole program as complication of the valve train and added weight didn’t provide a sufficient increase in power to warrant the change from conventional heads.

You've got to consider vehicle size, the 100 pound weight difference has to be multiplied by the reaction arm length from the vehicles' centers of rotation, so in real terms that 100 pounds is considerably more when it comes to dynamic reactions of the vehicle. This is why Grumpy steadfastly stayed with the SBC in his drag cars. The lesser weight times the lever arm of rotation far offset any power advantage that could be had from a big block in his chassis.

So in the end you've got to know what you’re building and how to optimize it.

But yeah if you built to the max of what’s doable using a 402 BBC and a 400 SBC, in the end the 402 would still be sucking air past where the 400 gave its’ last gasp.

The current issue of CHP has a dyno off between a classic Gen 1 SBC and a new LS. Now theory says that power is dependent upon displacement and RPM so two engines of the same size turning at the same RPM will develop the same power or more properly can do the same amount of work, regardless of their bore to stroke relationships. But as you move into the engineering details of these motors, you see that the tipped over valve angle and high ports of the LS do have a subtle advantage. While both engines produced extremely similar power and torque numbers the LS did it with about 10 degrees less cam duration and about 4 degrees less ignition advance. These are two things that make the engine more streetable in the case of less cam timing and better combustion characteristics and less power losses due to early ignition forces attempting to push the piston backwards. The unanswered question is whether or not the LS would have pushed more power with the same cam and ignition timing as the Gen 1. But alas, they didn't test for that.

Actually, the Gen 1 vs LS test says an awful lot of good about the Gen 1, and parrish the thought, the SB Ford Windsor as well. When you figure that these engines were designed about 53 and 48 years ago respectivly, using slide rules and drafting tables, it says a lot for the quality of the engineers and designers who produced what became such long lasting icons of their industry, and that these designs can still compete successfully against their 21st century replacements.

Bogie

I can say the 400sbc is i think the way to go I have one and it has not let me down by far the best motor ive ever had and snort and power is really good. build'em up and man i put 1600$ in my 400 and im about 430 440 horse and i could still do things to improve that will little bucks added a guy can build one to 670 hp on pump gas......  

i only skimmed the arguments you guys made, but this is my take. big block is so much easier to make power out of, but without aluminum heads, it will easily outweigh the small block. sbc can make all kinds of power... (hence why the corvette still uses a sbc design..) a BBC w/ aluminum heads, and mild work will outrun a modded SBC with iron heads, due to the even (or close) amount of weight so therefore, my choice is completely clear. (396/402 BBC FTW!!) lol just my take on things.

craig  

Corvettes still use small block Chevys?

That's news to me...  

the ls-x motors are based on a small block design yes?? iirc they have tiny heads and ports like the small block... not the big block. it is redesigned, i understand that, but it is loosely based off a SBC design. kinda like the quad4 and the ecotec. same but different...  

I guess you could say "loosely based"...

All I know is that an engine doesn't know if it's a big block or a small block. All I know is that the valve angles, port size, port location, and combustion chamber shape are all night and day different from the Gen I small block Chevy. I guess it's still on the same bore centers with the same pushrod and 2-valve configuration but the similarities end there.  

true. it also has the same cubic inch size, its shaped like a SBC, i think it was basically a rethought out small block. its a nice one, but why didnt they make an all aluminum BBC??? that would have been it for me. but no... no more big blocks. gay.  

They did make a all-aluminum big block Chevy, the ZL1...

Of course that is impossible to find but even then aluminum blocks are not all that spectacular. Horsepower losses are common just with the switch. A big block with aluminum heads can make enough power to offset the weight disadvantage to a small block Chevy.  

yup. thats what i was getting at. thats why i went with a BBC. its so much more power. its heavy, but who cares when you can open the hood and see that big ol' beast in there... but from a performance standpoint a big block is better IMHO. a small block is a 'consumer motor' you can get power AND mileage out of it. the same cant be said of a big block (at least it has yet to be proved to me)