What Is A Big Block? The Difference Between Big and Small Block Engines
Telling the difference between a big block and a small block engine can be confusing. Each has some pros and cons. Do you wonder why each type is called a big block or small block engine?
A big block engine is actually physically larger than a small block engine. Big blocks have a significantly larger diameter piston and make longer piston strokes. Big block engines are a Y block instead of a V block.
Facts about big block engines:
- Big block engines are physically larger
- Big blocks have a significantly larger diameter piston
- Big blocks make longer piston strokes
- Big blocks have bigger valves and ports
- Big blocks are made from thicker materials
- Big blocks are a Y block instead of a V block
- Big blocks were initially built for large passenger cars and trucks
This post is all about what makes an engine regarded as a big block.
What Makes an Engine a Big Block or a Small Block
Big block and small block describe two variations of V8 overhead valve engines. Big-block engines are physically larger than small-block engines but the real difference between the two is in the displacement (engine displacement is the measure of the cylinder volume swept by all of the pistons), size of bore, and stroke distance rather than just the size of the engine.
piston displacement Tmoore / CC BY-SA
“Big Block” was first coined as a term for a series of large displacement V8 engines that were developed by GM in the 1950s, and have been produced in the United States until 2009. As American-built automobiles grew in size following World War II, the engines they used had to become larger and more powerful.
Other manufacturers quickly followed suit to keep up with the large engines that GM was producing. The Chrysler B and RB engines are a series of big block V8 engines introduced in 1958.
The “FE” from Ford series big-block was introduced in 1958 as the 332 cubic inch V-8 with a 4.00-inch bore and a 3.30-inch stroke. The 332 debuted along with the 352 cubic inch big block. The displacement increase was accomplished by stroking the 332 to 3.50-inches.
Most often big blocks are known as having greater than 400 cubic inches with small blocks having less, but this isn’t always the case. A 396 Chevy is a big block motor while a 400 Chevy motor is a small block.
Big Block Engines Are Physically Larger
As a teenager learning about cars, one of the first things I learned was that there were three different types of motors that I needed to know about. The inline six cylinder in my dad’s farm pickup, the small block V8 that was in the family car, and the big blocks that were in the bigger hay hauling farm trucks.
Later I learned you could have a big block version for cars. These engines were in a class all by themselves. The power was already there, so you didn’t have to do a lot to get over 400 horsepower.
When you look under the hood of a car or truck you might immediately be able to tell if it’s a big block or small block just by the sheer size of the motor. The heads are noticeably wider and can be taller. As you look down the block will be wider and bigger overall.
The 454 big block Chevy “rat motor ” outweighs its little brother the small block “mouse” by approximately 130 pounds. This extra weight that the rat has over the mouse can be very noticeable if you are using an engine stand that isn’t rated heavy enough. Heres a picture of my big block rat.
Big blocks have a more square look, and their cylinders will typically be placed further away from each other. Though both engines are V-shaped, in a big block engine, that V looks more like a “Y” than not because of the additional space needed.
Aftermarket parts manufacturers have made it possible to put big block motors in place of small block motors in any truck you would want to. It is is a large market and they have made this engine swap into a simple process.
Big Block Engine Pistons Have Longer Strokes and Larger Valves and Ports
Each cylinder of an engine contains a piston, the distance that piston travels up and down in the cylinder is called the stroke. The shorter or small stroke makes it a small block where as the longer stroke makes it a big block. Shorter strokes makes higher revving possible and is why the small blocks typically can be revved much higher.
The diameter of the bore size of the engines cylinders also relate to if its a big or small block. The longer stroke will equate to the big block motor. Big bores equal better breathing, and small bores create more pressure, equaling more torque. Smaller bores do create limits on how high a motor can rev which many race engine builders find frustrating, but that is ideal for the large trucks that big block engines were first designed for.
A truck should have a large stroke to bore ratio for torque while a race car will have a small stroke to bore ratio for higher revving.
Big Block Engines Have a Thicker Built Y-Block Instead Of a V-Block
Big blocks are squarer, and typically will have cylinders placed further away from each other. Though both engine styles are V-shaped, in a big block engine, that V looks more like a “Y” because of the additional space needed.
The big block is used for larger passenger cars and trucks so they work harder, thus creating more heat. They are also cast larger to allow for the large piston bore that a big block requires. So looking at the front of the two engines you can see a noticeable difference in the width or girth of the big block.
Big Block Engines Were Initially Built For Large Passenger Cars And Trucks
The big block engine was originally built for extra horsepower in light trucks and passenger cars. Not only did it give the vehicles it was intended for extra horse power and torque, it won over the hearts of collectors and muscle car enthusiasts alike.
Introduced by GM in 1958 the Mark I or W engine as it was first named was built for the larger passenger cars and trucks that GM was building at this time. The small block motors with their lower torque ratings were not able to handle the heavier loads that all these vehicles were hauling.
The big block engine quickly grew in cubic inches and horse power over the years with the development of the 396, 427 and the 454. This quickly won over the GM car enthusiasts community as these became the most popular engines on the market.
After the 332 and 352 cubic inch big block motors, Ford introduced its 385 line of big blocks. The 385 engine family derives its name from the 3.85-inch crankshaft stroke of the 460 cubic-inch V8. Ford produced the engine in three displacements: 370, 429, and 460 cubic inches.
The Chrysler B and RB engines are a series of big block engines manufactured by Chrysler starting in 1958 to meet the competition of the other two large American manufacturers. The B and RB engines are often referred to as “wedge” engines because they use wedge-shaped combustion chambers. Chrysler built a long line of big block engines up until the end of 1978 when they ended production of the 440. The big block they will always be known for was the very popular 426 Hemi.
Final Thoughts
Now we know that big blocks are physically larger engines because of bigger heads and larger blocks. Big blocks have larger bores, longer strokes, bigger valves and ports and that can lead to truly astounding power production. They are normally a lower revving motor that creates more torque which is great for towing with trucks. Big block motors can also be built for higher revving high horsepower motors similar to that of a small block.
The Tool Box
Here is a great tool for helping you pull that engine. I know mine helps me get the right angle for dropping in my motors.
This is the engine stand that I use in my garage to set my engine on so I could start it on the floor. Just wire it up and get some gas to it and fire it up. Its a lot of fun to do in the winter when you cant be out driving your classic.
Related topics
Are big block engines still being made? GM stopped producing big blocks in 2009. Ford stopped production of big blocks in 1998. The last big block Chrysler engine was produced in August 1978; they were still standard in the 1978 Chrysler Newport and New Yorker. There are many aftermarket big block “crate motors”available on the market today.
Are big block replacement motors hard to find? If you are looking for a big block motor to drop in your classic truck you are in luck. You can find good donor motors at most wrecking yards that may or may not need freshened up. They often come up in Craigslist ads, Facebook ads etc. and there is a huge aftermarket of “crate motors” available.
Sources: wikipedia
Big block Chevy engines Mann, Dave (September 26, 2013)
automobilemag.com
The Auto Editors of Consumer Guide
“This is the difference between big and small blocks”, Hagerty
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