What Is A 350 Bored 60 Over? Understanding Engine Boring!

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what is a 350 bored 60 over

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Undoubtedly, the 350 is one of the most popular small-block engines in automotive history. This is due to its reliable performance, durability, and easy maintenance. Even better is that you can bore the engine at 60 over.

So, what is 350 bored 60 over? It is simply a modification made to a 350 cubic inch engine, common in most Chevrolet vehicles. The procedure involves increasing the diameter of each cylinder by 0.060 inches, resulting in a displacement of around 360.42 cubic inches.

But are there any advantages or disadvantages of boring a 350 engine? Stay here to find out, including what the modification comprises.

what is a 350 bored 60 over
Table of Contents

What Is A 350 Bored 60 Over?

This refers to a 350 cubic inch engine that has been modified by boring the cylinders 0.060 inches larger in diameter. It is done by cylinder boring/machining to make the cylinder walls bigger but more functional than the standard size.

The process also comprises installing oversized piston engines. Consequently, this helps increase the engine’s displacement.

Typically, a 350 engine is a 5.7-liter small block V8 with a stock stroke of 3.48 inches and about 4.0 inches bore. So, when this engine is bored 60 over, its bore becomes 4.06 inches, and the total displacement increases to 360.42 cubic inches.

The formula for calculating the total displacement is as follows:

(4.06in/2)^2 x pi (3.14159) x stroke x number of cylinders

In this case, the stroke is 3.48 inches, and the number of cylinders is 8 in a V8 engine. So, the calculation will be as follows:

(4.06in/2) squared x 3.14159 x 3.48in x 8= 360.42 cubic inches

However, boring a 350 cubic inch engine 60 over is only necessary under the following circumstances:

  • The engine is seizing or damaged due to overheating
  • The engine is experiencing a loss of horsepower
  • When rebuilding a worn-out or old engine
  • Pistons are damaged or seizing
  • You have excessive piston-to-cylinder wall clearance

What Does Boring a 350 Engine 60 Over Comprise?

Once you decide to have your 350 bored 60 over, disassemble the engine and take it to a machine shop that does boring. The mechanic will sonic-test the block first to determine the wall thickness of each cylinder.

If the thickness is sufficient, the mechanic will start the boring process using a boring bar to remove internal materials from the cylinders. This is done to enlarge the holes. However, some shops use a milling machine or a carbide cutting bit to bore out the engine.

Any Benefits of a 350 Bored 60 Over?

Increasing the engine displacement of your 350 to 360.42 cubic inches has several benefits. So far, I have come across most of these benefits also in the “What is a 350 bored 40 over” guide, and they include:

1. More Horsepower

Increasing the diameter of the cylinders allows more air in and out of the combustion chamber per cycle. And with more air, more fuel is needed, ensuring increased horsepower. Consequently, this lets you accelerate and reach top speeds quickly.

According to a Chevy owner, he got about 575 horsepower without reliability issues out of a 350 bored 60 over. Yet, the stock horsepower output of this engine ranges between 145 and 370 HP, depending on the year, make, and model of your vehicle.

2. Increased Torque

The 350 engine boasts about 380 pound-feet of stock torque. By increasing the cylinders’ size, you can potentially unlock greater torque. You could get about +10 ft.-lbs. torque, ensuring better hauling and towing capabilities.

3. Restores the Engine

If your 350-engine block is damaged or worn, boring it 60 over can restore it to its original specifications. I have found that this helps keep the rebuilding costs low while also increasing the engine’s performance.

While boring the engine, you could also replace the engine splash shield if it is worn out. But is engine splash shield necessary? Yes, because it ensures your 350 engine stays clean and dry by keeping water and mud off.

4. More Engine Modifications

Boring your 350 60 over allows the flexibility of doing other engine modifications in the process. Consequently, this helps save time and money. For example, I would suggest installing high-performance camshafts and exhaust systems for enhanced engine power during the boring operation.

5. Relatively Cheaper

Compared to buying a new block, the cost of boring a 350 cubic-inch engine is relatively lower. A new engine block can cost up to $8,000. However, the typical cost of boring a cylinder ranges from $400 to $1,500.

What Are The Cons Boring a 350 Engine 60 Over?

Although boring a 350 cubic inch engine 60 over has several benefits, it also comes with some drawbacks. Check them out.

1. Increased Fuel Consumption

When you bore your 350 cubic inch engine, this increases the overall cylinder volume. As a result, your car will consume more fuel, so it can produce the extra power.

2. Makes Cylinder Walls Thinner

Boring an engine generally causes the cylinder walls to thin and weaken. Over time, the engine may overheat in some cases due to the thin walls.

However, this problem happens only when the walls are not ultrasonically tested to determine their thickness level.

3. Limited Future Rebuilds

When you bore your engine 60 over, you remove a lot of materials from the cylinder walls, making them thinner. This usually limits the number of times you can rebore it in the future for rebuilds.

People Also Ask

In this section, I will respond to some commonly asked questions about 350 bored 60 over.

FAQ Gear Head New

Is it better to bore or stroke a 350 engine?

If you want extra horsepower, boring your 350 60 over is the best choice. But for increased fuel efficiency, it is better to stroke your 350 cubic inch engine.

Is a 350 bored 60 over safe for daily use?

Yes, if the machining work is done correctly by professionals and high-quality, oversized pistons are installed. However, you also must avoid certain driving habits like aggressive acceleration and high-speed driving.

How else can you increase horsepower in a 350-engine block?

Besides boring the cylinders 60 over, you can increase the engine’s horsepower by upgrading the air intake and exhaust systems. You could also change the valve train, stock heads, and camshafts.

Conclusion

A 350 engine bored 60 over involves increasing the cylinder’s diameter by 0.060 inches to boost the engine’s performance. However, there are disadvantages to boring your 350 60 over which you must take into account.

Having said that, boring a 350 or any other engine block can be a complex process that requires specialized tools. Unfortunately, these tools are pretty expensive. Therefore, you should leave the job to certified technicians if you want precise results.

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