dupe thread

 

I’m sure I should know what this means, but never paid attention.
If an engine has the same displacement, why is one called a small block and one is called a big block?
It came to mind as I was watching the auction

 

The size of the block is what they are talking about. The heads from a big block will not fit on a small block motor and visa versa.

 

I can understand that the heads wouldn’t fit one or the other. But, why would you want an engine that is physically (I’m guessing)
smaller (small block) in size and takes up less room, If that is even the case?

 

Generally smaller = less weight, easier to work on, more room for things like exhaust...

 

So this may show how "old school" I am, and maybe not kept up with the times I am not as familiar with the engines today and their designations/sizes.

Back in the day, the (GM) 350ci was the biggest displacement small block you could get. The 396ci was the smallest big block, and then there was the 427ci and the 454ci displacement big block.

The reason you could get a bigger displacement on the big blocks was that the bore centres on them were wider spaced, giving the opportunity to have a bigger hole for the piston. The block was therefore somewhat bigger, not sure what the outside dimensions were but it was longer and taller than the small block.

Small block - small displacement
Big Block - Big displacement

More displacement = MORE POWER!!

 

If that is the case, than why make big blocks?
If you could get the same displacement from a much smaller
engine, why?

 

The design (at least in the case of chevy's) engines big block vs small block are different. The big block chevy engine is a larger physically in length and in height, there widths are very close to the same deminsion.

Back in the day when these engines first came out we did not have the availability of parts to make them all that much bigger like we have today. Technology had not reached the point it is at today. As an example back in 1957 when chevy was using the old 283 and it was the biggest chevy V8 engine available, hot rodders could only do a very few things to this engine to make it bigger. In most case's we bored the 283 a full 1/8th of an inch or .125 and that gave us 301.782 cubic inches. That was a number that could not even be tried on later production blocks for many years. These 301 engines were great motors and in future years chevy built this same designed motor and same displacement by using 327 blocks and 283 cranks. There were machine company's ( very few by the way) that could off set grind a crank and thus get a little bit more stroke, but not much.

The first of the big block engines came in use in 1958, it was built for the chevy truck line as well as the heaver cars that they were building back then. It came in three displacements 348, 409 and the very rare Nascar version mystery engine 427. These were all "W" engines and had a very different form of combustion chamber that was not in the head but built into the block itself. These fell out of favor when Chevrolet introduced the engine we call today the Big Block with a much more conventional combustion chamber design.

Today this engine design can be taken to huge displacement numbers. I have one of these mountain motors in an old Hot Rod of mine and it is 632 cubic inches. I have heard of even bigger big blocks but have never seen one but there is a rumored 812 cubic inch motor.

Its not always inches that make the difference, some times its engine design and how they go about getting to those inches. Big Blocks and Big Inch--Small Blocks are not the same animal and behave in different ways to different mods. Both have advantages and dis-advantages.

RS

 

The thing is that the small block is putting out the same HP,
Maybe there is some modification to the small block to make it match the big block,
But that isn’t the impression I’m getting. The only thing I can tell is the displacement,
nothing more,
That makes sense to me. I have heard the term “THERE IS NO REPLACEMENT FOR DISPLACEMENT”
They must be using something to jack up that HP
I guess that is why my wife has a Nissan 370Z with a 6 pumping out stock 332HP stock. She doesn’t care, she just likes the way it looks

 

I can understand that the heads wouldn’t fit one or the other. But, why would you want an engine that is physically (I’m guessing)
smaller (small block) in size and takes up less room, If that is even the case?

Let's say you have a truck that has to pull a lot of weight. You would want a big motor that would last and last. Bigger is better in that case. If weight and size means nothing then the big block would be better. Heavy duty if you will. Big and strong.

Now if you want something to go fast you need to cut the weight down. A small block would be better. Like the one in your corvette. A smaller, lighter motor with the same horse power would be the ticket.

One is just as good as the other, it just depends on what you need.

That's all I got.

 

Thanks guys

now all i need is a week or so to figure out this entire thing

 

Big blocks have a heavier rotating assembly therefore more torque. The small block and big block could have the same hp numbers but the torque numbers are higher on the big block. When you increase the stroke on a small block the torque also increases, heavier rotating assembly. Back in 70 I had a 69 Camaro with a built 350, and my buddy had a 63 Nova with a .060 over 283= 292. Both cars weighed about the same, but his was faster than mine. I shifted at 7000 and he shifted at 9200 and that little 292 stayed together. We didn't have all the good go fast aftermarket parts back then. My sons car is almost 2 seconds faster with a 406 small block shifting at 6200. That 406 pulls harder than any big block I had back in the day. I'll take the large stroke small block any day.

 

I think Chevy had a 400 in the 70s that was still considered a small block.

 

Correct...

http://www.motortrend.com/features/c...ugh_the_years/

 

They did but they were truck or big car engines. They were very low performance. They were a large stroke short rod engine. You couldn't make one run with a 350 back then, no performance parts available for them. Now you can get anything you want for them. That's what I have in my sons car 406 ci. You couldn't put a cam large enough to get any performance out of them because the lobes would hit the rods. Now you can buy a small base circle cam as big as you want. The one I have put together has 13.8/1 compression pistons and 6" rods internally balanced and puts out 650 hp @ 6400. I had it in my 92 Grand Am tube chassis car. Now I have it in my sons 96 Firebird backhalf car.

 

Back in the day, you could have a drivers license at 16 with no restrictions.
When I was 17 I had a Charger 500 with a 426 hemi and 456 rear end.
I think that must have been a big block
It was so fast the first I drove with the go pedal smashed to the floor it was like I couldn't remember what just happened.
I don't know how my parents let me buy that thing.
Now back to our regularly scheduled program, I kind of got off topic.

 

HP is a theoretical figure that results from torque times RPM.

When you step on the gas, the acceleration you feel is torque, not HP.

As 92GA points out, you get more torque from a big block engine.

The reason why the built small blocks in his examples won races is because they had wider torque bands, which is to say that they were able to maintain torque as the RPM climbed.

This is the same principle Ferrari, etc. uses --small displacement engines that maintain their torque into the higher RPM range.

 

Yes, the 426 Hemi is a big block. Elephant motor.

 

It’s the same architecture as the current dragsters, and I’m sure funny cars well

 

I think that GM was the only car company that used the term big block & small block.