Why Does a Hemi Have 16 Spark Plugs?

Why Does a Hemi Have 16 Spark Plugs? Reasons and Benefits

Are you using a car with Hemi engines? And you are shocked when you hear that your Hemi engine has 16 spark plugs. And now you are interested in knowing the mystery behind these 16 spark plugs. Let’s solve your confusion!!

Engine designers design Hemi engines to have 16 spark plugs, with two plugs per cylinder, to make combustion faster, more complete, and cleaner. 16 spark plugs also help in providing more power and reducing emissions.

But the question is, why does Hemi make such a type of car engine design? While other engines mostly have 2 spark plugs per cylinder. Does it have some advantages, or is it just a marketing stunt? Before going into depth, first, discuss the design of the Hemi engine.

Hemi Engine

How Is the Hemi Engine Designed to Have Two Spark Plugs per Cylinder?

The word Hemi is the short form of the Hemispherical combustion chamber. The shape of the chamber is like a dome to facilitate combustion and a better flow of air and fuel.

The designers of the Hemi engine incorporated two spark plugs per cylinder, while most conventional engines feature only one spark plug per cylinder. Along with a dual spark plug, the Hemi engine also has intake valves, exhaust valves, Hydraulic lifters, and a cooling system that makes it unique and efficient.

Reasons Why Hemi Has 16 Spark Plugs?

The Hemi engine is designed so that it needs another spark plug to work correctly. The center of the cylinder is the most important place to install the spark plug. But so much space is occupied by valves, so there is no space in the center of the cylinder to put the spark plug.

The designers installed the spark plug in the corner of the cylinder, but it reduces the engine’s efficiency and causes incomplete combustion. To solve this problem, designers install two spark plugs in two diagonal corners of the cylinder.

Hemi Engine have 16 Sparkplugs

This method solves the problem of complete combustion and airflow, but this is not the ideal way to solve the problem. An efficient and reliable cylinder has one spark plug. But still, many cars use Hemi engines. Let’s come and discuss the reasons why some cars still use two spark plugs per cylinder.

Benefits of Having 16 Spark Plugs in Hemi Engine:

Using the Hemi engine, having 16 spark plugs has some advantages over other engines, including high engine efficiency, complete combustion, emission reduction, smooth driving, and more power. Some of those benefits are explained below.

1. Improved Combustion:

Two spark plugs can ignite the air/fuel mixture more efficiently and quickly, leading to complete combustion and improved engine performance.

2. Reduce Emission of Fuel:

Two spark plug in every cylinder increases fuel burning, ultimately resulting in low emission. The Hemi engine also has two valves per cylinder, allowing for better intake and exhaust flow through spark plugs—this design results in improved fuel efficiency and reduced emissions.

3. Increased Performance and Power:

With the 16 spark plugs, the Hemi engine is designed with a cooling system. This is the liquid cooling system in which liquid moves around the engine to absorb heat. So it prevents the overheating of the engine and increases its performance.

Drawbacks of 16 Spark Plugs:

Using the engine with 16 spark plugs does not necessarily make it more reliable. The engine’s reliability depends on many factors, such as the engine’s design, the quality of the spark plug, and maintenance.

The 16 spark plugs Hemi engine design is very complicated. So, it is difficult to find the exact problem and to repair it. The reason why repairing the 16-spark plug Hemi engine is expensive and time-consuming is because of its design.


1. Do All Hemi Engines Have 16 Spark Plugs?

No, not all Hemi engines have 16 spark plugs. Some Hemi engines, such as the 5.7L Hemi V8, only have 8 spark plugs.

2. Which Hemi Engines Have 16 Spark Plugs?

Main Hemi engines having 16 spark plugs are mentioned below:
Chrysler 426 Hemi
Mopar Hellephant
Toyota TRD NASCAR engine
Yamaha OX99-11

3. Does Having 16 Spark Plugs Make a Hemi Engine More Expensive?

Yes, having 16 spark plugs makes a Hemi engine more expensive than a conventional engine.


Hemi engines install 16 spark plugs in their design due to increased efficiency, quick burning of hydrocarbons, smooth driving, and decreased fuel emission.

But along with its disadvantages, modern cars don’t prefer to put 2 spark plugs per engine. That is why most 2000s cars have only one spark plug per cylinder. Two spark plugs per cylinder may become more popular shortly by making their design more efficient.

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