Small Block vs Big Block Engines: What’s The Difference?

There is an ongoing debate on the Internet about “small block” and “big block” engines that puzzle some car lovers. But, what is really the difference between a small and big block engines? You will be shocked at the truth about these engines, keep on reading!


Known also as “mouse” and “rat”, and “Turbo-Fire” and “Turbo-Jet” motors, the small and big block engines, respectively, are usually associated with Chevrolet engine series. This started out in the mid-1950s with the Chevy (Chevrolet) small-block ranged from the first 265 cubic inch (ci) in 1955. This article will tackle the difference between the small block engine vs the big block engine introduced by Chevrolet.

The man was surprised to drive the car

What is a “small block engine”?

Chevrolet is considered as the premier OEM (Original Equipment Manufacturer) concerning the differentiation of engine series, the company is believed to be the most successful on this field. The small block engine (commonly V8, that is, an 8-Valve model) that the company introduced in 1955 was continued until it was mass produced along with the 400ci in the 1970s.

The small block engine of Chevrolet had different variations in displacements (cubic inch- ci) which include the 262, 265, 267, 283, 302, 305, 307, 327, 350, and the 400 ci (6.55-liter) Chevy V8. These various displacements, however, were built with one standard to limit the diversity in parts, cost, tooling, and with the same dimensions.

But the most commonly built model was the 350-ci (5.7-liter) variant which accounted for more than 50% of the total production until 2003.

V8 engine

Here are some facts about the small block engine by Chevy

Before 1965, the small block V8 was the ideal engine for most Chevrolet cars. The Chevy 350-ci (5.7-liter) small block then became GM’s (General Motors) standard engine when manufacturing seized in 2003. However, as of this date, the small block engine is now being built in South America (primarily Mexico) as a crate engine for restoration and hot rod fanatics.

If you want to replace your small block engine and add more power to your car, you can order the Genuine GM (10067353) 350ci / 5.7L Gen 0 Engine, a product of GM Performance Parts, simply online (like Amazon.com). This crate engine is an authentic GM OEM rated at 195 Hp with 4-bolt main.

Automobile engine

What is a “big block engine”?

On the other hand, the big block engine of Chevrolet was first introduced in 1958 (the “U” series) and was basically designed for light trucks and large passenger cars.

Through the years, Chevrolet had introduced various displacements for its big block engines, such as the following: 348, 366, 396, 402, 409, 427, 454, 502, and 572 cubic-inch. The common displacement for passenger cars in the big block engine category of Chevrolet is the 348 to 454 ci variants which are still in use today.

The Chevy “W” Series of the big block engine was manufactured between 1958 and 1965. This engine was made from cast iron and has variations in displacements, such as the 348ci (5.7-liter), 409ci (6.702-liter), and the 427ci (6.9973-liter).

big block engine

Ford joined the “big block” bandwagon

In 1968, Ford started to offer the big block engine of their own starting with the 385 series. This series of engines was initially in 370-ci, 429-ci, and 460-ci varieties. Until the late 1990s, the 460-ci variant was utilized in trucks and other enormous applications.

Here are some unsolicited advice

For a big block crate engine, a terrific deal is the HPRE 454510 - Chevy Muscle Car 454 Crate Engine 510 Hp from HPREengines. This is a high-performance racing engine and is great for Chevy cars. Also available on Amazon.

Here is the good news, both crate engines (small and big blocks) we mentioned above have free shipping from Amazon Prime. Check specifications on this website and if any of those crate engines fit your requirements, order directly from Amazon (through this website) for a great deal!

Large engine of car

So, how the small and big block engines differ?

Aside from calling them the “mouse” and “rat” engines, the small block and big block engines have several distinguishable physical and dimensional characteristics. Among them are the following:

  • The big block engine is physically larger in size than the small block.
  • The small block engine has a smaller bore (or the diameter of the piston) than its big block counterpart.
  • The big block weighs much heavier.
  • The big block is taller and thicker than the small block engine.
  • The big block comes in both 2-bolt and 4-bolt mains, as opposed to the small block that has only a 2-bolt mains.
  • The big block engine was designed for larger passenger cars and light trucks.
  • Bore spacing (the distance between the center of one of the cylinder’s bores and the one next to it) in a big block engine is wider.
The man pours the oil into the engine


According to experts, as Ford, Chrysler, and other car manufacturers were also using the small block and big block engine series of their own years after Chevrolet introduced them to the world, there are no “big blocks” built today.

Automotive experts surmised that some manufacturers today do build vehicle engines larger than 400 cubic-inch in capacity but they are solely based on small block design and architecture or are a just clean piece of modern engines.

Please send us your comments if you have any question about this article and we are just glad to response.

By the way, if you are considering to buy a total replacement for your engine or you want to assemble your own and you need an engine, just consider these parameters:

  • The horsepower (Hp) you want
  • The number of valves
  • The piston diameter or bore
  • The displacement (cubic inch)

Then, all you have to do is to pick among the crate engines offered by Amazon.com (the better choice are the ones we mentioned above).


Hi there! I’m Jordan, chief editor of Crush the Road and I’m a self-confessed automative fanatic. Cars or vehicles has always been a passion of mine and will always be my favorite pastime. Now that I am married and has one adorable son, I have the time to write and share my personal experiences with other automative enthusiasts like me. Welcome to my fantastic blog!

Click Here to Leave a Comment Below 6 comments
Avatar for James Gilbert
James Gilbert - July 13, 2018

Nice and compact discussion…however, a mention of stroke as the variable in displacement for blocks with the same bore.

Avatar for Chris
Chris - November 18, 2018

A V8 engine refers to the number of cylinders and the configuration of the cylinder layout (two sets of four-cylinder engines in a V-shape). Every cylinder requires at least one inlet and one exhaust valve. So, simple mathematics will tell you that a V8 requires 16 valves at the bare minimum. You can’t be much of an “automotive enthusiast” if you don’t know the difference between valves and cylinders.If you need any further automotive engineering info, just drop me an e-mail.

Avatar for Sean
Sean - September 14, 2019


For a self-proclaimed “automotive fanatic”, you don’t seem to know some very basic car knowledge.

Second paragraph:
The “V” in “V8” does not stand for valve… It indicates the orientation of the cylinders / pistons.

Third paragraph:
The production was not “seized” in 2003, it was “ceased”.

Your whole “how do they differ” paragraph:
Can be summarized into “big block is bigger than small block” as you provide absolutely no useful information. there are quite a few important differences between the chevy big block and small block engines and you cover none of them.

For an “article” which is clearly just an advertisement (with referral IDs present in all of your links), you could have at least taken the time to provide a few useful bits of info and fact-check your content.

As it is, your “fantastic blog” is nothing more than a worthless money grab.

Avatar for Tom Hansen
Tom Hansen - October 15, 2019

I inherited a Chevy engine in a 1951 Ford, Dual 4 barrels, gear driven timing, that’s all I know. Engine #3970010…
also #T0123CKW, Turbo350 trans. positraction diff.
What do I have? Engine size? Year?
Thanks in advance for some info.

Avatar for joe flabeets
joe flabeets - November 25, 2019

small blocks HAD 4 bolt bottoms…change your comments about small blocks. HiPo and truck blocks had 4 bolt mains…check it out

Avatar for Donald A Wold
Donald A Wold - February 10, 2020

This is full of errors. There was never an 8 valve V8. The small-block DOES come with optional four-bolt main caps. Do your homework.


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