Built Sbc Vs Nearly Stock Bbc

Unforgiven

solid fixture here in the forum
Given that both engines have about 400 HP
Which engine would have lessor fuel consumption in the same vehicle.

First engine: An SBC that has been built up to make the power.

Second engine: A mainly stock 427 BBC

Both engines would be from the 60's...
And both engines would benifit from an EFI throttle body.
 
it should be close, the BIG BLOCK should be working less hard and in theory require less rpm, to make the 400 hp, but it weights about 100-150 lbs more
lets assume each engine makes 400 hp, that means the 427 is making about .94 hp per cubic inch, the 400 small block 1 hp per cubic inch
that means the 400 is making max power near 5252 rpm
the big block is probably closer to 4900 rpm
personally Id go BBC as its less likely to have maintenance issues in my opinion, and much more likely to pull a bit better with more low rpm torque ,
in the off idle to 3500 rpm range youll spend most of your time driving in.,
 
Last edited by a moderator:
I forgot about the weight difference.
But what you stated makes sense.
I was thinking about the cc differences in the heads. More cc's would require more air/fuel... But I
was not taking the stroke into account.
A smaller cubed engine is going to need to make more energy per cube to equal a larger displacement engine.
 
Last edited by a moderator:
I would say that if you built the 427 to make about 500 hp it would make up the difference in weight. It might use somewhat more fuel, but it would have a advantage in torque.
 
yeah it thats not all that hard, but why build a 427 when a 454 is most likely cheaper to build and has a bit more torque
 
I was just contemplating fuel needed in a given bore and chamber to make the same power.




but why build a 427 when a 454 is most likely cheaper to build and has a bit more torqu



Cause I only have this period correct badge

s-l400.jpg

:D:D:D:D
 
At one point in my career,
I had factory 421 fender badges on my 1965 tempest with a 496 BBC engine ,painted Pontiac blue ,
Chevy big block with a corvette tri=power air cleaner assembly with Pontiac 421 stickers
you would be amazed at how many people thought it was a Pontiac engine!
stickers and fender badges are hardly conclusive proof of what's in the engine compartment
l71ba.jpg

1965gtoside.jpg
 
Last edited:
yeah it thats not all that hard, but why build a 427 when a 454 is most likely cheaper to build and has a bit more torque
I agree, 454 would be better, a 781 or 049 head with 2.19/1.88 valves, do some bowl blending, gasket matching, unshroud the valves, maybe shave the heads, a good roller cam, get about 10:1 compression, you could make a good strong BBC. 500 or better horsepower would be pretty easy!
 
Well... last June (2020) I took the Camaro on an 850 mile trip and my 496 gave me 21.88 mpg highway on the last tank.
This was simply because it was properly tuned for the trip and I kept the RPM down.
Any well built and tuned motor will get surprising decent fuel milage.
 
I agree, 454 would be better, a 781 or 049 head with 2.19/1.88 valves, do some bowl blending, gasket matching, unshroud the valves, maybe shave the heads, a good roller cam, get about 10:1 compression, you could make a good strong BBC. 500 or better horsepower would be pretty easy!
How much $$ will all that cost you. A pair of Brodix RaceRite heads will be ~2500 and bolt directly in place... and takes a bite out out of the BBC weight.
 
it should be close, the BIG BLOCK should be working less hard and in theory require less rpm, to make the 400 hp, but it weights about 100-150 lbs more
lets assume each engine makes 400 hp, that means the 427 is making about .94 hp per cubic inch, the 400 small block 1 hp per cubic inch
that means the 400 is making max power near 5252 rpm
the big block is probably closer to 4900 rpm
personally Id go BBC as its less likely to have maintenance issues in my opinion, and much more likely to pull a bit better with more low rpm torque ,
in the off idle to 3500 rpm range youll spend most of your time driving in.,

All B.S. aside.... This was the type of reply I was looking for that Grumpy quoted above.
It was not about going with a bigger engine to achieve more torque or power.
The thread was about comparing fuel usage in two different bore sizes to make the same power.

I would think that there is a formula out there that states it takes " X amount of fuel and X amount of air" per CC to make 1 HP.

What would determine the total amount I think... would be the bore and stroke
 
All B.S. aside.... This was the type of reply I was looking for that Grumpy quoted above.
It was not about going with a bigger engine to achieve more torque or power.
The thread was about comparing fuel usage in two different bore sizes to make the same power.

I would think that there is a formula out there that states it takes " X amount of fuel and X amount of air" per CC to make 1 HP.

What would determine the total amount I think... would be the bore and stroke

I think there are too many variables to get that answer.

Smokey Yunick may have answered that in one of his books.
 
A bigger motor would generally have more pumping (and friction losses) at part throttle, although i personaly would choose a bigger motor if i could afford it :D
 
Back
Top