Right up front, the 400 is about 150lbs lighter than the 396.
I'm real happy with how well the SB400 performs in our 70 conv!

 

I'd say the BB .
Rpms .
The max hp is gonna show up later on the bb because of the cam .
More torque too because....well I'm not sure lol....just because it's a bb ???

 

I loved my 415 SB but I’m going to say BB because of the Canted valve layout.

 

How do canted valves make for more power ?
Serious question. I don't understand

 

The real key to who wins when rubber meets pavement though Is the entire combination.
Gearing , torque conversion , suspension, weight. The one with quite a few more ponies and or torque can end up in the dust

 

Chevrolet Engine Block Challenge - Hot Rod Magazine

We have a Chevrolet engine block challenge, pitting a 408-inch small-block up against a 408-inch big-block. - Hot Rod Magazine

www.motortrend.com

 

When in modern day magazines has any of them ever got it done at the track, other than Jim Moore?

 

Which engine makes more HP and TQ and why? Both

406 SBC SHP block
4.155 X 3.750
10.5 comp
234/238 @ .050 hyd roller
AFR 195 head competition version, 2.080 valve
Performer RPM air gap
750 Holley



404 BBC
4.135 X 3.766
10.5 comp
264/264/.619/108 solid lifter flat tappet
Ported GM heads 2.190/1.780
Performer RPM air gap
850 Holley

Well Mark, would I be correct to assume that YOU are the one who ported the heads on the BB engine? If so, then I'll say that the BB will make better power because you have a great reputation for your head porting work, and also because the valves on the BB heads are still larger than that of the SB heads, which would serve as a potential for better air flow,(which is why I think that the extent and the quality of the porting work on the BB heads is important in this comparison).

 

This is sort of apples to oranges.
How bout no hyd roller and no aftermarket block and heads?
All the sbc fans throw rocks at the bbc guys due to the extra weight.
But with the parameters above I’d say the sbc with its modern heads and cam.

 

Interesting quiz

If I had not read the thread on L-29 heads earlier today I would have put my money on the BB with ported heads and bigger cam. That combo seems capable of more rpm. SB seems like the rpm range would be lower given head size and cam.

Now Mark can tell us why what we think is obvious is wrong and why.

 

The 406 peaked @ 5900, the 396 peaked @ 6100, BUT the dyno I use shows a lower HP peak than my dyno, about 300 RPM less, so you have to figure that in.

 

Theres no question the BBC heads flow more, theres no question the BBC cam is worth power.

 

How is it possible one of these engine makes considerably more power than the other? Bore and stroke is basically the same, air flow similar, similar intake manifolds, and so on..........................

 

How is it possible that the 396 only peaked at 6100 rpm with a cam that big?
Why did it drop 30hp at 6200?

 

The dyno I test on reads 300-400 RPM low on the HP peak. The dyno was set to stop @ 6100 RPM, @ 6200 the dyno was pulling the engine down.

 

I’m going to say the small block has a better ring package and lighter valve train. 8mm vs 3/8”. Roller more efficient under the curve. Makes more peak hp.

 

Based on past experience the same size SFT in the 406 would be worth 20 HP over the 234/238 HYD roller.

 

Why so low?
An acquaintance would turn his 396 about 7800 with a Crane cam close to those spec except rectangle port heads and tunnel ram.

 

404 BBC, why? better flowing heads, better cam specs and most of all better able to carry the power over the curve for a better ET and MPH. I still like the 406 though, it just needs some better parts to keep up with the 406 IMO.

 

Which engine makes more HP and TQ and why? Both
406 SBC SHP block
4.155 X 3.750
10.5 comp
234/238 @ .050 hyd roller
AFR 195 head competition version, 2.080 valve
Performer RPM air gap
750 Holley
404 BBC
4.135 X 3.766
10.5 comp
264/264/.619/108 solid lifter flat tappet
Ported GM heads 2.190/1.780
Performer RPM air gap
850 Holley

Based upon exactly which heads are ported I think the BBC should have a higher torque amount & a flatter torque curve and carry the torque further in the RPM range. But the 406 should have a slightly higher power peak by about 10. IDK that's just a guess.

 

Big block more torque due to weight of internals and the ability to flow more air in the higher rpms

That 406 small block will be no slouch with those small ports. It will run out of air in higher RPMs but that low rpm’s would give the BB a run for its money down low.

 

OK

The 406 SBC made
559 HP and 560TQ


The 404 BBC made
550 HP and 513 TQ

I used to sell a 406 with a production block and a 258 @ .050 solid flat tappet cam, and AFR 195 heads, they would make 581 HP and 560 TQ. I've always said a 406 can get on a lot of BBC builds, the question is: How does this happen?

 

Don’t know how but the 400 just works. I had a similar internal balanced 415 with a 254/262@.050 solid roller with Dart sportsman heads. Unfortunately never on a dyno but was a terror on the streets.

 

Guess the sbc was better optimized correct cam selection.
Sbc heads must flow better with smaller ports.

BB with that 264/264 cam I figured it was going to pull more then 7000 rpm’s . It seems like it would be over cammed for that size engine. Wonder what would happen if the BB was cammed with a similar cam as the small block.

 

Guess the sbc was better optimized correct cam selection.
Sbc heads must flow better with smaller ports.

BB with that 264/264 cam I figured it was going to pull more then 7000 rpm’s . It seems like it would be over cammed for that size engine. Wonder what would happen if the BB was cammed with a similar cam as the small block.

In your opinion what do you think this over camel 396 would run in my 3600 pound chenille in the 1/4 mile?

 

My guess is less reciprocating mass in the small block.

 

FINALLY

This is exactly what I think, I left out one specification when I started the thread, the bob weight, 1500 for the SBC and 2200 for the 396, then theres the crank and balancer weight.

 

If the chevelle was set up great
I would think somewhere in the low 11 second range min a street driven car and somewhere in the 10’s for a strip duty

 

That 264° cam in the BB is really throwing a monkey wrench into the mix for me--assuming the rest of the peripherals were up to snuff, I'd expect that cam to peak closer to 7K in a 400" engine. (It'd be interesting to see that engine tested with about 16° less intake duration and 8° less exhaust duration)

2 other things: what size headers & collectors (and extensions?) were used on each engine, and were the bores notched on the 396?

 

Again it won't peak high on this dyno, its a weird dyno it peaks low. The headers on this dyno are weird, but you have to use his headers thats how the dyno is setup, if the the engine was tested on my dyno it would peak @ 6500-6600 RPM, if I ran this engine my car I'd gear to go through @ 7200 RPM. I'm happy with the power, my customer is happy with the power. 6600 RPM seems to be where my closed chamber headed dual plane intake engines peak.

 

It may turn et’s from 10.60’s in a nhra stocker with race trans & converter to slower if ran in a normally geared car.
My personal car peaks a bit over 7000 with a shelf roller cam ,ret port head and 410”.

What’s an iron head,alum intake bbc weigh?

 

Wow a boat load was said on this one i am no engineer physics major or high fallootin wizard . i am just an old school retired machinist . Heres my two cents . The 400 sbc is maybe 160 lbs lighter than a BBC. The 400sbc will makeBB torque earlier . That being said everything is in the combination of parts . We are not talking your average street beater here we are talking a well built engine with really good innards and outers like Afr,s etc and fancy bottom ends . I have done many engines in my day both SBC AND BBC amongst others MOPARS and FORDS. I had some garages and service station customers that had race cars . My claim to fame was building potent bullet proof street beaters for the kids and was very sucessfull at that . the only dyno i had was the seat of the pantaloons meter, for me that worked well but here is my thoughts on an all out effort with both engines using really good parts balancing and top flight machine work i think the BBC will come out ahead on the dyno . That being said on the street is another issue a half century ago i had seen many a street race at various locals that the driver made a huge difference in the outcome even when the other car had more power some were engines i built others were engines built by some of my competitor machine shops. i had one really good customer and friend no longer with us MIKEY D i would put that kid in the RONNY SOX category on the 4 speed he was a good driver from start to finish. that kid could hop into a V W and out run a double a fuel dragster this of course is an exageration but he was that good.and thats the rant of an old man .ALEX

 

I am wondering with a smaller cam the BBC would make more power (than what it did) due to the fact the 264 cam is large for it and your dynamic compression (more of a 12 to 1 compression type cam) is way down there. The port velocity of the SBC must be very good with that size port and cubic inches. I agree with a guy above I thought the BBC would have peaked higher I have same duration cam in my 540 (hydraulic roller) and it peaks at like 6300. I think it is not all about the flow but flow and port velocity.

 

Is it possible that they both do at different rpm.
The small block at lower because of less weight to get things moving.
But, the big block in the end because of the extra rotating weight keeping a momentum.

 

How fast would the 400 sbc run with tuned up non vortec heads stock rods ?
Say like a fuelie head and modest budget?

 

I did a 406 one time with a Isky 280 mega cam with 441 heads ported, can't remember the power but it was over 500 HP.