Vettelaw

Maybe this is a dumb question, but I'll give it a shot anyway.

What is the major technical differences between the small blocks vs. the big block engines?

I know that BBs usually come with larger displacement (427, 454) but I've also heard of some SBs having a displacement in the 430-range. :confused:

I really can't figure it out, maybe you guys can help.

thejaf

Other than the size of the blocks? :lol:

The heads are bigger (chambers, valves, runners, etc) on a big block

jimduchek

They're different engines. A small block 283 and a small block 427 are still 'the same engine', just bored/stroked differently, etc. Parts from one will fit the other. With the exception of the distributor, big block Chevy parts don't fit small block Chevy's -- they're different engines. The difference that is most notable is, of course, size. A SBC intake will fit any SBC (this is actually not true these days, but pretend it is for the time being), because the intake ports are basically the same on all the heads made for SBC. Same with exhaust -- those headers or manifolds will fit any heads. (Once again, this is not entirely true with the new generation small blocks, some aftermarket heads, etc, but pretend with me). However, these parts simply would not fit a BBC. The 'big' and 'small' notation has nothing directly to do with engine displacement (although, obviously, big blocks are much larger usually, because small displacement engines with big ports are a bad idea). But you can certainly have a 396 big block and a 427 small block. :)

Another note that gets asked a lot, 'rat motor' and 'mouse motor' are often used to refer to 'big block Chevy' and 'small block Chevy'...

Jim

ScubaJKD

The difference is the owners. BB guys always want to talk about torq. SB guys always want to talk about revvvs. :lol:

Mack

Yeah... And big block guys think size counts, while small block guys think agility is more important. :D

ScubaJKD

Hmmmmmmmm :lol:

427V8

Well there may not be any dumb questions but there sure are al LOT of Dumb Answers!

Basically a big block is a higher performance version of the small block. It was made to be stronger and to flow better than the small block.

A big block has more room between the clyinders for larger pistons, a Higher deck for a longer stroke and bigger heads to flow better. The cam is bigger and raised for a bigger stroke.

It was made for torque torque and torque!

427V8

LMAO, No Monty,
Don't worry I LOVE mice!

Larry B.

You HAVE to drive a big block to appreciate it! Small blocks perform very good and certainly are the engine of choice for most people. No doubt that a late model small block will out perform a stock big block but it doesn't feel that way when you are driving the big block. Instant throttle responce (AKA torque) any speed. This may be the 21st century but there is something about being able the out run lots of todays hot cars with a STOCK 32 year old beast that is handicapped on todays 93 octane fuel. AND It get lots of looks.

Shutdown1

......1969 was a good year.


'74 Turbocharged 350, "Molested to Perfection", class of '71

Techno

The 454 is a stroked 427.
The biggest difference is the heads/valve configuration. This is where the term "porcupine"heads comes from. All the valves in a BB are canted to allow better breathing. On most engines the valves are just poked straight down.
If you see a pic of the valves you can see all of them tilt one way or the other. Intake canted to reduce the 90 * curve from the intake to cylinder, the same for the exhaust.
The cast exhaust "semi-headers" are unique ( I think) to Corvette BBs and the price reflects this.

454s use a balance weight on the flywheel to compensate for the additional stroke. These engines are externaly balanced. They also have the bottom of the cylinders scalloped out for the crank throw.
BBs also have different porting choices, oval or square. Sqaure is for high rpm use- better breathing, this is at the cost of low rpm torque. Off course the oval heads have better low speed response at the expense of high rpm use.

The oiling system is probly different also- don't remember. You can tell a 4 bolt main from a 2 bolt by the additional tappings above the oil filter, this is a 4 bolt.

The BBs also go larger. The casting is a different animal and becomes siamese bores where the cylinders touch between pairs, no cooling passage between them. Then they make another jump and re-cast the whole thing larger. These are usually tractor or boat engines that may need 1,000+ from each engine.
BBs are usually considered low revving engines compared to SBs this is for the most part true. You can build a high revving BB though and some of the 'Vettes have a high red line indicating this.

If you compare a SB to a BB it usually is a unfair comparision. The lighter SB is usually tricked out to obtain the higher #s. A mild BB can get this and still be built to exceed this.
The last and most important, You can't get torque from less cubes. If you super charge a SB the HP goes high but try down shifting in one as compared to a BB. It just ain't there!

I have drove/ridden my brothers C-5 auto and if my car had a, what 6 speed? that slipped until the engine reached 6,000 rpm it would take off too!


[Modified by Techno, 9:59 PM 12/10/2001]


[Modified by Techno, 10:05 PM 12/10/2001]

Lohkay

:lol: :lol: :lol: :lol: shudown...I laughed on that one.

Chuck Harmon

Monty,

I think you are the one who has gone over to the Dark Side! You've been hanging around Merlin too long. :smash: 1400hp twin turbo?

I think it was Hans Morgenthau who said "Power corrupts, absolute power corrupts absolutely!"

Chuck

p.s No need to convince me that you have close to an honest 700hp with the larger pipes!

Techno

I disagree with your milage point. I don't think the engine size has very much to do with your mileage. I'm willing to guess that you have a highway rear end. In the 70s and up the biggest thing they did was drop the ratio to improve milage. This is why there are 6 speed trannys and why trucks still get lousy milage.
For the torque. While it may be true 2 engines can get the same amount. It' s not true at what rpm they get it at.
This is one mistake I see alot of people making is building a race engine when they will be driving it on the street
If your getting 700 hp from a SB without any induction charging system apparently you and I have different views on a streetable car.

To make matters worse. I could build a Cadillac based engine that would wiegh about the same as a SB and put out 500hp to 1400 hp at 11,000 rpm - I wouldn't consider the last to be streetable though. The Caddy engine wieghs only 60 lbs more than a SB. Throw some alluminum at it and there would be little difference.
Or go the other way and stick an off the shelf 200 lb Mercury drag engine 2.5 liter 380+ hp.
Thats about 400lbs less than a SB. All you have to do is mix you fuel.

Not to start an argument though.

ZD75blue

this is the kind of thread that i drop my own opinions and preconcived notions and try to learn something... i'm all ears

ZD

bence13_33

Monty:
(If this is none of my business, please don't hesitate to say "it's none of your business)

Just out of curiousity, how much money did that 700HP SBC set you back?

bamavettes

This is not 1969, but how about 1968. It's hard to beat a good rat.

L71

whats nice about a rat is that you could pull one out of an old station wagon and with a few cheap mods go head to head with any expensively done up small block

67HEAVEN

Or more importantly, big block guys win....small block guys.... :jester


[Modified by 67HEAVEN, 8:33 PM 12/10/2001]

Shutdown1

.....Geeez man, I can't believe all this. Everybody knows the difference between a big block and a small block it that a big block leaves no room in your engine compartment to get to anything, goes through $20 worth of gas before you get to third gear, uses a quart of oil a day, and cranks out so much heat you have to drive with the air conditioning on in the wintertime. Any other "technical" description of a big block is meandering hypothesis. Regards. Thanks Lohkay!


'74 Turbocharged 350, "Molested to Perfection", class of '71