Difference Between Chevy 400 Small Block and 350?

Difference Between Chevy 400 Small Block and 350?
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Do you need clarification on Chevy 400 and 350 Small Block engines? Today I am going to compare them so you can determine which one fits your requirement better.

400 and 350 are small block engines by General Motors that power several passenger vehicles and pickup trucks. The engines are famous for their cost-effectiveness, performance, and fuel economy.

It may be tricky for an ordinary car owner to pick between these two since they share the same block design. But some key differences might prompt you to swing in favor of one or the other. Chevy 400 is more about horsepower, while the 350 can give you decent performance and fuel economy.

But apart from this, there are some crucial differences in both engines’ designs, components, and manufacturing. Let’s dig deep and find out which one is the better option.


Chevy 400 Small Block Engine

The 400 small blocks first appeared in the 1970s in big passenger cars and mid-size trucks. As the name suggests, it has an engine displacement of 400 cubic inches and can generate up to 265 horsepower, enough for a mini SUV or a truck.

Here are some key specifications of the Chevy 400:

1. Dimensions

The Chevy 400 carries the same form factor as its predecessor from GM V8 series engines. It measures roughly 28 x 26 x 27 inches, but the displacement is higher, thanks to the smaller internal dimensions. At 575 pounds, the weight is also similar to previous small-block engines

2. Power Output

Initially, SBC 400 was designed to be a high-torque engine with a slightly lower RPM. It was achieved by a long stroke size and two/four-barrel carburetor.

According to old measurements, the engine offered a gross horsepower of 265, which translates into 150 modern horsepower.

3. Internal Components

Externally, SBC 400 looks like just another tiny block engine, but the company has redesigned the internals to give it higher power while maintaining the same size.

  • The bore size has been increased to 4.12 inches to achieve a higher displacement. It also increased the overall stroke to 3.75 inches, meaning while the engine maintains the same length of small block 350, the removal is more elevated at over 400 cubic inches.
  • Block size is the same as previous small block engines, but the company has redesigned the cast to achieve higher displacement.
  • The shared water jackets were removed to achieve the ⅛ inch bore diameter. Also, A larger crankshaft of 2.65 inches, higher than SBC 350, was introduced.
  • SBC 400 features smaller connecting rods than SBC 350.  It resulted in higher vibrations which the designers fixed with a harmonic balancer and a flexplate.


Chevy 350 Small Block Engine

Chevy 350 is the older of the two engines and was introduced way back in 1955. Since then, these powerhouse engines have been used in several small/medium-sized vehicles, family cars, small pickup trucks, and even small-sized boats.

1. Dimensions

The external size of the engine is the same as SBC 400. With a 28 x 26 x 27 inches length, this engine could replace any engine, including Chevy 400.  The company has manufactured as many as 17 variants of SBC 350. One of the most striking features of this engine was that it’s so easily interchangeable.

Many internals, including connecting rods, pistons, and bores, can easily fit into any 350 engine. It’s something to consider if you are looking for an economical fuel engine for your old V8 350 vehicle.

2. Power Output

Compared to Chevy 400, the 350 is intended to be a higher RPM engine (approximately 4600 RPM). The engine produces 330 foot-pounds of torque and 255 horsepower in standard conditions, translating into 145-147 net HP. However, the output has varied over the years between 145 to 370 HP.

3. Internals

  • The engine has a bore size of 4.00 inches, slightly smaller compared to SBC 400. It translates into a shorter 3.4-inch stroke, giving it a higher RPM and torque.
  • A smaller 2.45 inches crankshaft with flexplate and harmonic balancer to reduce the vibrations from higher RPM.
  • Larger 5.7-inch connecting rods, compared to the 5.56-inch used in SBC 400.


Chevy 400 Small Block Vs 350: Head-to-Head

Let’s see which engine appears to be on top in terms of power, fuel economy, and cost:

1. Power

The Chevy 400 is a clear winner in terms of power and performance. Due to smaller internals, the engine has a higher displacement means it’s suitable for towing, hill climbing, and large-size sedans.

The 350, on the other hand, offers decent power, but it fluctuates in different engine variants. The engine was designed to be a commercial product rather than a luxury one.

2. Longevity

Sports car or a family sedan, we always want a reliable engine that doesn’t leave us pushing our car in the forest. Both 400 and 350 are durable engines and maintain a decent power-to-reliability ratio.

No surprises here; the Chevy 350 is a more reliable engine and is supposed to last longer. The more powerful 400 is a better option for off-road driving, towing, etc. It also has a better loading capacity, reducing the engine’s lifespan.

3. Fuel Economy

Naturally, the more powerful 400 is not a fuel-friendly engine. The higher horsepower translates into higher fuel consumption. But this is the case with every single powerful car on the planet.

The 350, in comparison, is a better option if you are looking for an economical fuel engine and are ready to trade a little bit of performance for that. Another thing to remember is that the 350 is better off with premium fuel to maintain performance and economy.

4. Cost/Overall Value

The SBC 400 will cost you around $3000, and the installation should take another $2500-$3500, including replacements and removal.

On the other hand, you can get the job done for somewhere between $1000-4000 to replace and install a Chevy 350 engine entirely.


Final Word

GM V8, Small Block engines, are some of the oldest modern engines and are often considered the best manufactured by the company. The difference in performance is not drastic, but the 350 provides a good value for money.

Ultimately, it all comes down to your personal preference and requirement. If you need an engine for your loading vehicle or long off-road trips, go with the 400. You are better off with the commercially successful Chevy 350 powerhouse for any other purpose.


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