i forgot to mention, the 400 is a '76 with stock heads, and both the 350 and 400 are 2 bolt mains.

 

It depends on what you want to do with the car. 350s and 400s will make plenty of power for most people (especially the 400). Small blocks are generally cheaper, they tend to fit better (though just about anything is going to fit under the hood of that Impala) and they are lighter. You already have the blocks so thats a good starting point. The crank on that 400 may be able to be ground down. If not, you can find new cast cranks for 350s and 400s for about the same price it's going to cost to have one machined. Dont underestimate the two bolt blocks, they'll take more punishment than a lot of people say they will. In fact, many people prefer the two bolt 400s.

If you're looking for a lot of power on 87 octane then maybe a 454 would be the way to go. It's just going to suck a lot of gas doing it.

Hypothetical situation.

The fuel cost for a 10mpg 400 that burns 92 octane gas at $3.00/gal is going to work out to about 30 cents per mile.

An 8mpg 454 burning 87 octane at $2.70/gal is going to cost about 33 cents per mile to drive.

Even though the 400 in this case burns higher priced gas is actually cheaper than the 454 burning the cheaper gas. I dont know what you are actually planning on doing but thats just something to keep in mind.

Since you said one of your concerns is your budget I'd suggest you go with the 400 and slap on a set of aftermarket Iron heads. Aftermarket heads for small blocks are pretty reasonably priced and will make a lot more power than the stockers you have now. The 400 will provide more grunt for that big car than a 350 would but it will be a little easier on gas than the big block will be.

 

Blazin72... Has some good cost effective base numbers for sure... It does matter though what your going to do with the car...? Its heavy and the BBC will have the torque to move it quite well but the cost is a factor unless you do some good & careful scrounging...? You have 2 SBC`s to start with and I assume the car was setup for one...? Alot of things to consider but really comes down a personal preferance and how resourceful you are...? (access to parts and how much $$$ is availible...?)

Heavy car I like the BBC but most budgets say SBC...

 

All I can tell you is once you go Big Block you won't go back! :thumbup:

 

The 400 would be the cheaper alternative, since the 350 spun 3 main bearings then it`ll need align bored, which runs up the price greatly.
I`d go with the 400 anyways. they make good torque and your wagon needs all the torque it can get to help move it around.

 

A 400 sbc with a set of vortec heads can out torque a 454 in the lower rpms. I have seen a few 87 octane dyno pulls with 406's making 500+ ftlb of torque at low low rpms. However, those setups only made power to 4000 or 4500 rpms at which point, a BBC will torque curve will pull away. A high torque 400 would be perfect for a 2.73 or 3.08 geared impala.

 

Check this out: http://chevyhiperformance.com/techarticles/148_0401_imp/

 

A 400 sbc with a set of vortec heads can out torque a 454 in the lower rpms. I have seen a few 87 octane dyno pulls with 406's making 500+ ftlb of torque at low low rpms. However, those setups only made power to 4000 or 4500 rpms at which point, a BBC will torque curve will pull away. A high torque 400 would be perfect for a 2.73 or 3.08 geared impala.

Nope, nope, I gotta dissagree on that. Take a look at this desktop dyno chart. This is for a fairly plain 454. I know Desktop Dyno is not dead on acurate but it will but you in the ball park. Look at the what the toruqe is and where is starts. I don't believe your 400 will do that.

http://www.bigblock67chevelle.com/454.JPG

 

In the Chevy article you posted they said this. " We finally called it quits with a torque peak of 529 lb-ft at 4,100 rpm and 490 hp at 5,600 rpm ". The 454 I posted with stock heads was makeing that much toruqe at 2000 RPM.

 

Nope, nope, I gotta dissagree on that. Take a look at this desktop dyno chart. This is for a fairly plain 454. I know Desktop Dyno is not dead on acurate but it will but you in the ball park. Look at the what the toruqe is and where is starts. I don't believe your 400 will do that.

http://www.bigblock67chevelle.com/454.JPG

I agree with your dissagreement. It's hard to beat the torque of a 454 :thumbup:

 

it is plain and simple, small blocks are for showing, but the big blocks are for going, this is of course, in stock form.

 

I like the BBC arguement, but a well built SBC is hard to beat from a price standpoint. My dad races a smallblock (junk motor, cast everything), the most expensive part are the Vortec heads. He has gotten into the low 13's here at 4200 feet. That motor tends to want to rev, not ideal for what you want. The 400 would be a good torque motor and not provide the extra weight of a BBC. Just depends on what you have on hand and/or what you can get easily.

 

hmmm

One important issue to remember is MONEY. The BBC will cost alot more to build than the sbc and in the end you wont do any better than a sbc if your trying to run 87 octane. 3 questions will help you narrow it down... Whats my budget? How do I plan to use the car? Will I try to sell it anytime soon?

 

:thumbup: :thumbup: NOTHING REPLACES DISPLACEMENT :thumbup: :thumbup:

502 CUBES will not leave you saying to yourself damn I should have gone bigger


HOW FAST YOU GO ALL DEPENDS ON HOW FAT YOUR WALLET IS

SR66 :thumbup:

 

I would have to say after my personal experience upgrading from a small block to a big block, there are several advantages and disadvantages of both. The BBC has a weight and cost penalty, so you will have to factor in such things as a likely spring (suspension) and motor mount change. This will cost in the 2-300 dollar range on top of the additonal parts cost. I did not change the fron springs, and although the ride ehight only dropped about an inch, I have to be careful of botooming out on country roads. OUCH!
On the plus side, the car feels very responsive in comparison to your better than average 350 4 bolt with ported camel hump heads and a reasonably healthy cam. I squeezed my 350 to 11: 1 with block decking, head shaving and flatops. The car had a great high rpm pull that you would have to spend a lot of money on a big block to do. I have done the same thing to the big block 454 I am currently running. Forged flattops with a decked block and shaved heads to get it to about 9.2 :1. 781 cast iron heads with a pocket porting. The car is way more responsive feeling at low rpms without a doubt, but tops out at about 5800 rpm. It's more about grunt than that slingshot effect a smallblock has. You also get the advantage of being able to run highway gears instead of 4.11's to make a 3000+ lb car move. my 2 bits.

 

454 all the way.

68

 

well, i got a 427 for it, im not sure if it really is (didnt run the numbers) but it was recently rebuilt, .030 over, double roller timing set, performer intake, steel crank, came with the flywheel and all the acessory brackets too! also has PASS heads and on the block it says 'hi perf pass.' i pulled the pan and could see honing marks all the way up the cyls.

best thing of all i got it for 600$, the total to drop it in with headers, new gaskets, waterpump/fuel pump, belts, hoses etc was about 900.


only question now, is how long will the turbo 350 hold up, a 4L80 might be in the near future.

 

Sounds like a good combination. You will be surprised how strong that turbo 350 is. I ran one behind a supercharged 454 for several years with no problems,(street car), and I drove the snot out of it.
Bob

 

I have a BBC and I like them (eventhrough it will get 7mpg if driven hard). But don't be so sure at any BBC will out torque any SBC. The 406 sbc with vortec heads makes BBC torque even in the low rpms.

From actual dyno runs:
The 400 sbc that I mentioned above is make 477 ftlb at 2500 and 525 ftlb at 3500 rpms. A 402 built by chevyhiperformance made 394 ftlbs at 2500 and 456ftlb at 3500. The 406 sbc kicked the 402 bbc in low rpm and mid range torque.

Also on Edlebrock's dyno page they list a 454 Performer making 450 ftlbs at 2500 and 470 ftlbs at 3500 rpm. Still the 406 sbc was making more toque.

Again on Edlebrocks site, the 454 performer rpm made 390 ftlb at 2500 rpm and 520 at 3500. Still less torque than the 406 with vortec heads at low rpms.

These runs were made on acutal dynos. Sure there can be variations in dyno's but I would trust the numbers more than desk top dyno.

Look at the numbers, the 406 with vortecs makes huge low end torque.

 

One thing you missed. The example I used for Desktop dyno was useing STOCK heads and still beating the SB's.

 

Well, desk top dyno is nice, but I prefer real dyno results if they are available. I have run that program more than a couple of times and I'm sure my 454 doesn't make 550 ftlbs at 2000 rpm as it always tells me.

But with published dyno pulls......477 ftlbs at 2500 rpm and 525 ftlb at 3500 rpm is heavy duty low end torque for any engine, big block or small block. 70 to 80 ftlbs more than a 396bbc at the same rpms with a 400sbc is doing something.

 

What was the compresion ratio of the 406 vs the 402??

68

 

I don't know. But those engine were built and tested by the same magazine chevyhiperformance.com. Go check out the site and click on the old tech articles. But I do know the sbc was built for 87 octane.

 

Desktop Dyno is full of S H ! T!

I know considering I built a 496 BBC and used desktop dyno to help me pick a cam.
http://www.off-road.com/chevy/tech/454engine/
http://www.off-road.com/chevy/reviews/comp/

I was expecting huge torque numbers but was dissappointed when I went to a real dyno and saw my numbers were much lower than expected. At least the 406 article used a real dyno for real numbers. Also, the 406 is at a lower compression and can run on pump gas where the Desktop Dyno shows 10.5:1.

I don't even bother using Desktop Dyno to help me make decisions any longer.

A BBC can produce good torque but a 406 is right up there in numbers and is lighter and cheaper to build. Just take a look at the cost on new heads and tell me which one is a better deal. Aftermarket parts seam to be more available for a sbc than a bbc.

Also, BBC's are known for chewing up rear cam lobes.
http://www.off-road.com/chevy/reviews/bbc_oiler/

I'm now going back and bulding something similar the the Impersonator 406sbc with the AFR heads. I've been a huge BBC fan but the costs on building a SBC that performs just as good as a BBC is why I'm choosing a SBC for my next build.

If I was building strictly a drag car, then I would be looking at doing a 540+ BBC or a turbo 400sbc. Just take a look at what the SBF's are doing with the large turbo's.

 

I'm planning a 496 build and I would like to know what the engine did on the real Dyno.

As far as chewing up rear cam lobes It's never happened to me (knock on wood).