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What Do Duramax Cylinder Numbers Mean?


by Ian Nicholls


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If you’re searching for Duramax engine diesel, you may be confused about the cylinder numbering.

Understanding Duramax engine cylinder numbers can be difficult for many people. However, knowing the basics of cylinder numbers can help you quickly fix issues with your Duramax engine cylinder. 

The good news is that Duramax cylinder numbering is not complicated. So long as you know the location of the cylinder, you can easily find the right parts regardless of how it’s numbered.

Have no idea about the location of the Duramax diesel cylinder numbers of your engine? Don’t worry. In this guide, I’ll help you understand the basics of Duramax cylinder numbers. Let’s get started.

What Do Duramax Cylinder Numbers Mean?

The back of the cylinder engine is the side connected to the transmission, while the front of the engine has the belt. The front of the cylinder engine is considered cylinder number one. The engine’s end is regarded as the front of the engine, and it’s where the cylinder numbering starts. 

Typically, the front of the engine is considered cylinder number one.

The cylinders are numbered from number one(at the front of the engine) to eight at the back such that the cylinder rods connect to the crankshaft. It’s a straightforward system that’s easy to understand and repair when necessary. 

The crankshaft of the Duramax cylinder is kept in the center, and the numbers are on two sides. 

The left is the driver’s side, and the right is the passenger’s. On each side, there are four cylinders, hence eight cylinder numbers. 

The Duramax cylinder order goes from front to back such that numbers 1,3,5 and 7 are on the right, while 2,4,6, and 8 are on the left. 

Note that there is No, and I repeat, there is No direct opposition between cylinders 1,3,5, &7 and 2,4,6, & 8. 


The right and the left cylinder banks are offset from each other, with the left cylinder bank slightly behind the right bank. It’s complex and expensive for cylinders(in ordinary auto engines) to connect to the crankshaft directly opposite each other. Therefore, they’re not connected directly opposite each other.

The connection between cylinder two and the crankshaft is right behind cylinder one. It is then followed by the main bearing, then cylinders three, four, another bearing, and so on. This allows the cylinder rods to connect correctly to the crankshaft.

For better understanding, I’ll explore more on these numbers. All Duramax models, particularly 6.6 models, follow the standard numbering system; check out the following models.

  • 3.0 Duramax cylinder numbers 1,3,5 and 7 reside on the passenger side, while numbers 2,4,6, and 8 reside on the driver’s side. 
  • LB7 cylinder numbers include 1,3,5, 7 on the passenger side and 2,4,6 and 8 on the driver’s side.
  • I5p Duramax cylinder numbers include 2,4,6, 8 on the driver’s side and 1,3,5 and 7 on the passenger side.

Watch the video given below for a better understanding.

2 Types of Duramax Firing Order

Firing order refers to the sequence or order in which the cylinders of an internal combustion engine ignite and deliver power. 

Engine cylinders don’t fire in the order of 1-2-3-4-5-6-7-8. If they fire this way, the crankshaft could deform or break. While there are several Duramax cylinder orders, the general firing order follows the sequence of 1-2-7-8-4-5-6-3. Below are different types of Duramax firing orders.

1. Stock Duramax firing order. The stock firing order is arranged such that the twisting/torsional moment is uniform and the load is evenly distributed longitudinally on the crankshaft. Duramax cylinder firing order is 1-2-7-8-4-5-6-3, and if the engine is left completely stock, the firing order isn’t too problematic. 

Many diesel owners modify their engines for more power, which alters their stability. Increasing power capacity and Revolutions Per Minute(RPM) causes the crankshaft’s front end to wear out. Ultimately, the stock firing order becomes a liability and weakens the crankshaft further. 

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2. Alternate Duramax firing order. If you face issues with the stock Duramax firing order, you can change the firing order to 1-5-6-3-4-2-7-8. This is known as the alternate firing order. The most typical reason for modifying the firing order is to relieve stress on the front part of the crankshaft in high-performing applications.

When you change the firing order, you’ll have effectively changed the harmonic frequencies and vibrations, which finally reduces stress at the crankshaft.

Duramax cylinder engines respond to alternate firing orders better than any other diesel on the market.

In stock firing order, the firing order ends at cylinder three and starts again through cylinders 1 and 2. Hence, the crankshaft bears the most strain and tends to break behind the first rod.

However, with alternating firing order, cylinders one, two, and three are placed away from each other, distributing the stress more evenly. 


Wrapping It Up

In this article, I’ve explored the essential details of Duramax cylinder numbers. I’m confident that you can now locate your engine’s cylinder numbers, identify any issues and take the necessary steps to fix them.

Duramax cylinder numbering follows a standard order based on the position of the crankshaft. If you’re on the front side, numbers 2,4,6 and 8 are located on the driver’s side, and numbers 1,3,5, and 7 are on the passenger side. 

If you still have questions regarding your 6.6 Duramax cylinder numbers or any other Duramax model, contact us today.


How Are The Cylinders Numbered On A Duramax?

The cylinder numbers are arranged in a simple system. They are numbered from one at the front of the engine(passenger side)all through to cylinder eight at the back of the engine. They are arranged such that the cylinder rods connect to the crankshaft. Cylinders 1,3,5 and 7 are on the passenger’s side, while cylinders 2,4,6 and 8 are on the driver’s side.

Where Is Cylinder 3 On A Duramax?

On a Duramax, cylinders 1,3,5, and 7 are on the right side(passenger side), while cylinders 2,4,6, and 8 are on the left side(driver’s side). Therefore, cylinder 3 is on the right-hand side, second from the front.

Where Is the Number 6 Glow Plug on Duramax?

On Duramax, the number 6 glow plug is on the left-hand side(driver’s side), and it’s the third plug from behind. 

Where Is Number 8 Cylinder on a Duramax?

Cylinder number 8 on a Duramax is on the left-hand side(driver’s side), and it’s aligned toward the firewall(bulkhead).

Ian Nicholls

Ian is a seasoned automobile enthusiast with a knack for diagnostics and repair. Adept at overseeing garage operations, skilled in troubleshooting, and passionate about ensuring top-notch vehicle performance.

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