Ok, I don't want to start a debate on whether SB or BB is better. I just want to know the differences between the two (SB400 and BB402).

I mean, both have the same bore size, the crank stroke is almost the same (3.75 vs 3.76), and the rod length doesn't make much difference really (6" SB aftermarket vs BB 6.135")...

I don't know big blocks at all, and I will go that route eventually, but I don't have the money for a BB conversion at the moment. I know they can make more power, but is it only because of their larger displacement, heads, and larger valves?

In that case, in the 400 vs 402 example, since they share so many features, wouldn't the 402 make more HP because of their larger valves/heads, and the 400 make more bottom end torque because of the smaller valves/heads?

Remember, I don't want to start a SB vs BB war...

years ago i remember a shoot out between these two motors and at the final result the bbc won by a few tenths in the 1/4 mile, they had the same profile for each motor as close as one could make it, intake, carb, comp, cam profile..........

the installed the motor in the same car with the same set up.........

granted i think they spent a few 100 more dollars on the bbc to build.......

i myself like the look of the bbc under the hood,i would go with the bbc if i had the choice..........

Originally posted by Fried_Guy:
I don't know big blocks at all, and I will go that route eventually, but I don't have the money for a BB conversion at the moment. I know they can make more power, but is it only because of their larger displacement, heads, and larger valves?
I think the heads are the largest difference, the BBC will breathe alot better because of the valve angles(and valve size) with all else being equal.

As a die hard big block fan, I'm gonna say the SBC is the better choice for a street/strip application. The SBC 400 will almost always make more torque (at least at the lower rpms), given the same basic guidelines, due to the smaller intake runners. The heads on the big block are often too big a 402, they do flow more, but you can get more than enough velocity and flow with a good aftermarket head, with a small port to boot. The big block can accept a larger lift camshaft compared to the small block. So with the larger high flow heads, and larger camshaft, the big block will almost always have more top end horse power (given the same basic guidelines). But the deciding factor why the SBC is a better choice IMO, is the weight. The SBC is a good 200 lbs lighter. That combined with a more usable torque curve on a daily basis and cheaper parts, I personally would go SBC in this case. I think if your gonna convert to a big block, go big or go home.

To get into this AND hopefully NOT stir the long running emotional debate!!

A 402 BB should run peanut port heads to be about equal to a 400 with 200 cc heads! And even then, the stock, 2.06"/1.72" BB valves are way bigger then the 2.02"/1.60" SB valves....

Then the lift should be equalized between the two due to the rocker arm ratio's being different IF you want to get knit-picky which I think we should..

Then to flip the coin to the other side, I wish a pair of almost identical motors would be tested with the SB running the "mini BB, splayed-valve" heads so the heads would be approximately the same design at least!!

pdq67

A big block does not weigh 200 lbs more than a small block. The reason I choose big block, you can do more with less,it don't take much to get a big block to run good. Intake,cam,carb and headers and you have a respectable runner,no smallblock will run with a big block unless a head swap is involved.

Also as a big block owner and devotee, I must say there is an advantage the small block has, other than overall weight and cost of parts plus ease of obtaining parts. The rotating weight and internal friction is less, which costs power. So the equal cube BB has to make up that deficit before gaining a power advantage by better breathing.

weight difference between a BBC and SBC is 150 lbs..

I race with a friend with a 71 velle 030 402 ret port heads 8" converter,411 gear and a small roller cam.3750lbs with driver goes 11.20@118 no spray with mufflers on unleaded.simple and cheap combo.I'm not sure if a 400 sbc would do that with a set of sportsmans and good cam in it.

if we were talking 400sb vs. 454 then i agree with the bbc guys, but i don't see many 402's that i couldn't dust with a warmed over 355, let alone a warmed over 406! my 71 Chevelle with bbc race weight: 3920lbs, sbc iron heads race weight: 3760lbs. so there's 160lbs difference in motors, now the most important thing to me is that the sbc has a lighter rotating assembly and much lighter valvetrain. i'd take any 355+ cube small block over the 396/402 any day. and the magazine that did that 402 vs 400 test was also using production heads on the 400 and Merlins on the 402, so it, as usual when it comes to mags, wasn't a very fair comparison. they'll make about the same power similarly equiped, but the 400 is at least 160lbs lighter, and will rev quicker due to lighter rotating assembly and lighter valvetrain, IMO.

I'm not so sure that Merlins are any better than 049's or 781's....BBMike is using Merlins,and I'm using stock 049's...I've got him by 7 tenths,although i'm running a solid cam,but a small one,got him by a few cubes too ;) ...I'd still take a BBC any day.

bla bla bla............stock bottom end unbalanced 396 with the 30 year old bolts included, pressed on a set of trw pistons 350 bucks, threw in a stock zl-1 cam used with lifters 90 bucks, with stock heads that was backyard ported 100 bucks to regrind valves,and threw on a 75 dollar torker intake and 160 dollar 850 holley with 79 summit headers and ran 11.20's at 121 mph running that thing at 7000 rpms for years ...........in a 3600 lbs car do that with a small block 400............

money is on a bbc bone stock bottom end handle way more then a sbc can.......

i don't want to get into a pissing contest with anyone over this, but that combo shouldn't run anywhere near that time, high 11's at best, IMO. i had alot more motor than that in my 71, and it didn't run that good. 11.40's was all mine would run and it was a 454. it did weigh about 300lbs more though. if i had the 454 parts in a 396 it would've been lucky to get into the 11's at all. most warmed over 396's only run low 12's high 11's in a Chevelle, from what i've seen in my 18 years of drag racing.

you're probably right Robert about the Merlins on a small cube bbc, but what if the 400sb would've gotten to use some aftermarket heads too? it's no secret that you need aftermarket heads to make real power with a small block. some good heads would've upped the power on the 400 at least 50-75hp, and there was only like 1 tenth of a second difference in the times as they were. ;)

I am on the fence as I own and like both. I think that they both have there own advantages. The BBC is heavier but has better factory heads, while the small block is usally cheaper to build and lighter. If you are talking about the HOT ROD 408 comparo of Aug 98, the small block had ported sportman 2 heads on it.

Well Casey, hopefully the replies answered your question. The replies also gave you a little taste of the wide range of results that can be had from certain engine/car combos. Before any one gets too excited about a simple cheap no nitrous 3,750 lb 402 BB Chevelle that goes 11.20's at 118 mph, just do the math about the hp level that such results would need. What I'm trying to say is that the devil is in the details that go unsaid - like for sure that is not a hydraulic roller street friendly engine, not is the total setup likely to be a good mannered street car. Point is that it is all a trade off - you may just find that your 406 delivers most of what you want in performance.

Good luck, Thomas

why would it be hard to believe.....12 to 1 motor with a 262/273 @.050 with .561/.600 lift with a .016 valve lash,open headers,with a 4500 stall and 4.56 gears with 28.5x10.5 slicks.shifting at 7000 rpms and going thru the lights at 7200 rpms with a locked out dist. set at 36 degrees....using th350 tranny and 10 bolt.....

pissing contest lol :D crower roller 258/264 .587/.600 lift 10" of vacuum,valve springs lasted 2 years driven 6o miles a week.L2240nf-030 pistons 3/8 rods good bolts cast crank.goes 133 on a 175 shot@ 9.98 isn't even dead hooking yet. :D motors 12 years old

if we're talking about that radical of a motor then yes, a 406 could easily obtain those times with that much cam, compression, and convertor. i know several that are in the 10's like that, but not with stock heads. you will definately need aftermarket heads to do it with a sbc.
sorry about doubting that it could run that, but i should've asked the question of whether it's a pump gas street motor. that's all i have a use for, so it's kind of imbedded in my brain. :D
Stret cars are all i'll mess with. if i can't drive it as well as race it, then i don't want it. ;)

Sorry I haven't replied in a while... I've been quite busy.

Basically what I get out of this is 50/50... and from my experience on this board, when that usually happens the differences are minimal if any at all.

I see the advantages of the BB and the SB now and never doubted my decision to go SB... I just wanted to know for the sake of knowing.

I'm not knocking BBs or SBs, because I have respect for any well-built engine. Especially if it's a chevy ;)

Thanks for all your replys and for not turning this into a shooting gallery.

Small block power... no, wait, scratch that... CHEVY POWER! graemlins/thumbsup.gif

yes it was a gas pump motor 92 octane with a bottle of 104 booster thrown in on race das for just in case...... and it was driven on the street and back to forth from work and even went on a few road trips and it got 11 mpg on the highway driving it at 55-60mph..........i drove it to the track, put the slicks on(after taking them out the back seat, pulled the exhaust off, empty the trunk full of tools and go racing. drove that motor from 96 to 2002 in about the same basic mold...some things were changed only for faster but the hard parts was mostly left there alone.....