Is A Pontiac 400 A Big Block Engine? What’s The Difference Between Big Block and Small Block?

The Pontiac 400 was an iconic engine in its time and one of the most powerful ones that Pontiac produced. But is a Pontiac 400 a big block engine? We checked it out for you.

The Pontiac 400 was a powerful engine. It was produced from 1964 to 1979 by Pontiac and was used in numerous vehicles like Grand Prix, Bonne Ville, and Firebird. 

It produced almost 335 horsepower in vehicles which were considered the most powerful ones of their time. So, is Pontiac 400 a big block? No, Pontaic 400 is not a big block engine. It is a single small block engine.

Is A Pontiac 400 A Big Block Engine

What is a Big Block Engine? 

The engine block is the primary part of an internal combustion engine. It comprises the cylinder, crankcase, oil filter, coolant passages, and many more components.

The big block engines are noted for larger bore(piston diameter), big valves, and long stroke(distance traveled by the piston from top dead center to bottom dead center). So, they produce more power compared to small block engines. These engines even look physically large and even have more weight. It can generate almost 5500 rpm.

The big block engine was earlier designed for large vehicles like trucks before being introduced into passenger cars. It put a lot of pressure on the front axle because of its heavy weight. So it becomes challenging to accelerate the vehicle.

The first version of the big block engine was initialized in 1958 and was of the U series. It was mainly capable of producing power in light trucks and some passenger cars. 

Later W series was initialized in the market from 1958 to 1965. The engine primarily consists of cast iron, and there were three displacement options, i.e., 348,409 and 427 cubic inches.

Also Read: 350 Bored 30 Over HP: Unleashing Maximum Performance for Your Engine

Understanding the Difference Between Big Block and Small Block Engines 

#1. Weight

The weight of a big block engine is high as it consists of more metal and large cylinders. The engine assembly is approximately 685 pounds.

The small block engine weighs approximately 575 pounds. They also have metal and cylinders but fewer in number than big block engines.

#2. RPM

Big block engines generally come with 5500 rpm, whereas small block engines have a bit higher, i.e., 5800 rpm.

#3. Fuel Consumption

Fuel consumption is higher in big block engines because it has larger cylinders. But small block engines have fewer cylinders and are also small. So they don’t consume much fuel.

#4. Cost

The cost of a big block engine is higher compared to a small block engine.

#5. Acceleration And Handling

Big block engines are heavy. But they produce more torque and power, which aids in overcoming the limitations of being heavyweight. Now, if we talk about small block engines, they are lower in weight. So you can handle the vehicle more easily, and the car accelerates more.

Is A Pontiac 400 A Big Block Engine

 #6. Piston

Big block engines usually have pistons of larger bores and strokes, and it results in large displacement. But small block engines have pistons with large bores and small strokes, resulting in small displacement.

#7. Wheel Size 

Big block engines require large wheel sizes. They even cover up larger spaces because of more number of cylinders. The cylinders are even quite large. Small block engines require a small wheel size. They need little space because of less number of cylinders.

#8. Displacement

It is the volume of the cylinder. If an engine has more cylinder volume, it will add more air and fuel to the combustion chamber. It is usually expressed in cubic inches or liters. For example, if we say that the engine displacement is 400 cubic inches, it is equivalent to a 6L volume.

Big block engines have an engine displacement of more than 400 cubic inches. But there are a few exceptions. For instance, if we talk about Chevy 396 engine doesn’t have a displacement of above 400 cubic inches. But its engine is known as a big block because of its architecture.

Old and small block engines had an engine displacement of less than 400 cubic inches. But now the displacement is increased because of additional airflow.

#9. Size And Shape

The big block engines have cylinders placed far from each other to increase air circulation. So they resemble more like a Y shape rather than a V shape. Now, if we talk about small block engines, their pistons are arranged to almost like a V shape.

Pros and Cons of Big Block vs Small Block Engines

Big Block Small Block
  • Big block engines have larger strokes, bores, and valves. So the vehicle’s engine runs fast and hard and delivers more power.
  • Big block engines last for many years. 
  • These engines are capable of producing more torque.
  • Provide higher displacement compared to small block engines
  • Easy to handle and accelerate because of its lightweight.
  • Not much expensive
  • The engine requires less fuel in each revolution. So overall, they consume less fuel.
  • Lightweight
  • Big block engines are made from different metals. So they are heavy.
  • They consume more fuel.
  • Due to its heavy weight, you will find it challenging to handle and accelerate.
  • The cost of a big block engine is a bit high.
  • Small block engines have few cylinders. They even are of small size. So they produce high power like big block engines.

About the Pontiac 400

Pontiac’s history dates back to 1965 GTO, but it was officially recognized in 1968. In 1955 Pontaic was selling over-the-counter components that the dealer or owner could install. 

The GTO purchaser can buy these counter components to increase the vehicle’s performance. It consists of a steel pan with a gasket and hood scoop. Cars equipped with a four-barrel carburetor and tri-power engines can take advantage of this package.

Pontiac Engineers started working hard in 1967 to meet up with Chevrolet and Mopar. They increased the bore size by 0.030 inches and the displacement to 400 cubic inches. They even changed the valve size and cylinder head by reducing the piston valve angle.

The intake manifold design was also improved in 1967, capable of generating high torque at low speed.

Is A Pontiac 400 A Big Block Engine

The ram air was first time showcased in Pontaic Brochure in 1968. Additionally, in May 1968, Pontiac introduced a new cylinder head and round exhaust port. These heads could enhance the exhaust flow by almost 10 percent compared to the D port cylinder head.

Pontiac introduced two upgraded ram air engines in 1969. Ram air 1V was one of the most powerful versions of the Pontiac 400, which can easily be marked by round and upgraded cylinder heads.

The Pontiac 400 generated 370 HP in GTO trim and 345 HP in small Firebird, which made them the most powerful car for almost ten years.

What Was Special About The Pontiac 400? 

The 389 block engine used in Catalina, GTO, and Lemans produces 330 horsepower. But when Pontiac 400 was used in cars equipped with a four-barrel carburetor, it had 360 horsepower, which was relatively high in the 1960s and 1970s.

Pontiac is quite famous for its Ram air versions which had five total stages. The Engineers first set up the Ram air version in 1967. They slightly changed the camshaft, cylinder head, and exhaust manifold and even included a hood scoop.

These changes reduced exhaust back pressure and enhanced the intake efficiency.

In 1968 Pontaic introduced Ram air 11. The primary difference between Ram air 1 and Ram air 11 is the cylinder head port shape. The D shape port was changed to round one in Ram air 11.

Later in 1969, Pontaic launched two versions of the Ram air engine. The Ram air 111(400 cubic inches V8) engine had D port heads. But Ram air1V has a round port head and made slight changes in the design of the intake ports. The final one was Ram air engine V, but unfortunately, it was never used in production.

It was looking to make three versions of the engine. The first one is a 303 cubic inches short deck engine in a Trans arm car (1969) for participating in SCCA trans arm competition. The second one is a 366 cubic inches engine that can be used in NASCAR. The third one is 400 cubic inches for producing Firebirds.

Pontiac Engineers produced various intakes for vehicles equipped with single and dual four-barrel carburetors.

The Ram Air V blocks were quite heavy, and only 303 and 400 cubic inches engines were decided to be used for production. Unfortunately, in 1970 the SCCATrans arm rules and regulations were changed, so the project was dead. 

Later Ram air V blocks of 400 cubic engines became also a victim of a bad time. The RPO had permitted operating such an engine, but the vendor became bankrupt and was given the duty of producing special rods. It is estimated that less than 500 Ram air V 400 cubic engine swerve was produced then.

Was The Pontiac 400 Big Block?

Pontiac 389 was quite famous in the 1960s NASCAR. But in 1967, the Engineers made slight changes in the bore and incurred the engine displacement. The Pontian 400 engine could produce more power than Pontaic 389 and became immensely popular for its other benefits. 

But, Pontiac 400 is a single small block engine. The external dimensions of all its V8 engines, i.e., from 326 to 455 cubic inches, are almost identical.

Most people think of the Pontaic 400 as a big block engine because of its higher displacement. But in reality, it is considered a medium size level engine. It cannot produce enough torque and power like a large engine.

Is A Pontiac 400 A Big Block Engine

Frequently Asked Questions 

#1. Did Pontiac make a big block 400?

Pontiac produced a single small block V 8 engine without adding a larger block which differs from all other manufacturers. 

The external measurement of all the V8 engines starting from 5.3 to 7.5 L, are almost similar.

#2. Is a Pontiac 400 and a 455 on the same block?

Both Pontiac 400 and Pontaic 455 are equipped with V8 engines. But they are not similar because Pontiac 400 has an engine displacement of 400 cubic inches, but Pontiac 455 has 455 cubic inches.

Secondly, Pontaic 400 produces power of 335 Horsepower. But Pontaic 455 generates 360 Horsepower.

#3. What engine is in the 400?

In 1967 Pontaic made slight changes in the 389 cubic inches engine. It slightly increased the bore and raised the engine displacement to 400 cubic inches. 

The bore or diameter of the piston is 4.12 inches, and the stroke of the Pontaic 400 is 3.75 inches which is almost similar to Chevy’s big block 396 engine.

Is A Pontiac 400 A Big Block Engine

Wrap Up

The Pontiac V8 engine was manufactured by the Pontiac division of General Motor Corporation between 1955 to 1981. In the 1960s, Pontiac 389 was quite popular. Later the engineers made slight changes in the diameter of the piston and raised the engine displacement to 400.

The majority of people think Pontaic 400 as a big block engine. But it is a small block engine. All the Pontiac V8 engines are small blocks with similar connecting rod lengths, i.e., 6.625 inches.

Photo of author

Sean Mendez

Hi, I am Sean, a self-confessed petrolhead. I live in Boise, Idaho with a busy family of four and our energetic Labrador retriever. Thank you for visiting my website. You can find my email on the contact page.

Leave a Comment