Camshaft overview by an experienced mechanic

The engine is what's responsible for carrying the whole vehicle. For this engine to work effectively, several components have to work seamlessly with each other. Believe it or not, all components — big and small — are critical to the vehicle's overall efficiency.

A fault in one small part, let's say the camshaft, can cause your car engine not to run. The camshaft is one of the several critical components that are required for a combustion engine to work. Remove camshafts from your engine and you have a car that will neither run nor start.

So, what is a camshaft and why is it so important to automobile engines? To answer these questions and more, we've enlisted the expert help of a seasoned ASE-certified mechanic. Everything you read from here onward are the words of a mechanic who's been fixing cars for more than 20 years. Let's begin.



A camshaft is basically a simple cylindrical rod (or shaft) running the length of the cylinder bank. Shaped lobes are positioned along with it, and they are referred to as cam lobes. The camshaft working is attained with the number of cams on the shaft. One lobe for every valve.

They are typically found directly above the cylinder banks where they control the functions of the inlet and exhaust valves. Their calibration directly controls the amount of air-fuel mixture that the inlet valve lets into the chamber.

In the same vein, it also determines how effectively the waste gases from the initial ignition are expelled from the chamber. Effectively, it influences the efficiency of the next charge.

How it works

To simplify, we'll have to start at the beginning: understanding the basic workings of the internal combustion (IC) engine. The IC engine has seen more refinement and development than just about any other mechanical process in the world. And the camshaft has been a founding component right from the beginning.

To start the engine, the inlet valve allows in the mixture of air and fuel (also referred to as the charge). This mixture is subsequently ignited inside a cylinder. It's at this point that explosive energy is generated and then converted into kinetic energy through the camshaft, crankshaft, pistons, and transmission.

Simple as it may seem, it's actually an extremely complex system of parts. When the shaft rotates, the cam enables it to act upon a valve or switch to a degree equal to the severity of its shape.

To put it simply, the speed of its rotation will determine the rate of action. In modern internal combustion engines, camshafts work to control valve timing. To ensure this timing, engine camshafts are linked via a timing belt or a timing chain to the turning of the crankshaft as it directly moves the pistons inside the cylinder.

The shape of the cam itself is meticulously designed to control the rate at which the inlet and the exhaust valves open and close respectively. This phenomenon is commonly known as variable valve timing. This makes camshafts not only critical to the working of the engine, but they also go far to influence its performance.

Components of camshaft

camshaft parts

Camshaft as a component of a four-stroke engine is in turn made up of sub-components. That's how machines work, components are made up of components. The following are the major parts of a camshaft:


The lobes go into rotational motion as the piston begins its vertical (up and down) motion. The function of the lobes is simple and straightforward. It works to open and close the intake and exhaust valves respectively. The engine speed determines the speed of the cam ones.

Main Journals

The power generated by the camshaft results from a constant rotational motion. The journals function primarily to keep the camshaft rooted while it carries out its spins about the bay of the car engine.


The anterior end of the camshaft is made to bear the belt that connects it to the crankshaft. While the posterior end turns the engine's distributor using special gear. Together with the rest of the engine, the ignition timing is in tune with this posterior end.


The bearings are mounted together with the main journals. Its job is to shield the camshaft from causing damage to the engine block should the engine become faulty. Bearings are essentially there to ensure that the rotational motion of the camshaft is as seamless as required.

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What material is it made of?

The material from which a camshaft is made is the most important detail if you hope to avoid premature wear and inefficient performance. Camshafts are manufactured using cast irons or steel.

Chilled iron cast camshafts are the best. While they may be more expensive, their wear resistance is considerably higher than any other type of cast iron or steel for that matter. Steel is also good as far as the type of steel used matches with the cam follower it will run against.

Camshaft vs. Crankshaft

Camshaft vs. Crankshaft

As you may have already guessed, they are not the same thing even though they sound almost alike. They are, however, interlinked and are both important components of the engine.

On one hand, a camshaft meters the opening and closing of the engine valve at the rate of one can per valve. Crankshaft on the other hand converts the vertical (up and down) movement of the pistons into rotational motion which is to be passed through to the flywheel and then the transmission motion.

Crankshaft and Camshaft working mechanism

What causes a camshaft to go bad?

Many problems can develop on the camshaft. If left unattended it can cause damage to the engine. The following are the major causes of camshaft failure:

Excessive wear

This mostly refers to when the cam lobes wear out too soon. It's often a result of poor camshaft break-in. High Valve Spring Pressure is another reason cam lobes may suffer quick wear.

This is especially true for high-performance race engines that require high spring pressure to work with their high-lift cams. It doesn't really matter because cars like these are built for high performance, not longevity.

Mechanical interference

When the moving parts of a camshaft are not given enough room, things can begin to wear and tear. Apart from the limited range of motion leading to parts crashing into each other, camshaft damage can also result from excessive heat buildup.

Cracked camshaft

In some unusual cases, the camshaft itself suffers a crack and break. This can be caused by the following:

  •       A different component of the engine, the connective rod, for instance, coming loose and ramming the camshaft. E.g. valve to the piston, retainer to seal, rocker arm slot to stud interference.
  •       Defective camshaft. This could result from improper handling during packaging, shipping, or installation which may leave late damage that will manifest later.

Camshaft replacement

The next thing to do once your camshaft becomes bad is to replace it. There's the temptation to want to fix it by yourself but don't. Seeing as replacing the camshaft is complex and can easily be done wrong, an ASE certified mechanic should do the job.


The cost of replacing a camshaft varies with the car type. On average, it can cost anything between $1500 - $3000, including workmanship costs. The camshaft itself doesn't cost so much, the bulk of the expense goes to labor.

Camshaft position sensor

Camshaft position sensor

This is an electro-mechanical device that monitors the position and the speed of the camshaft. It, in turn, relays collected data to the engine control module (ECM) of the automobile.

It's this fed data that the ECM uses to control the amount of fuel that enters the internal combustion chamber and the accurate ignition timing to ignite the air-fuel mixture.

Besides helping the camshaft, and by extension the whole engine, to function efficiently, the camshaft sensor also notifies you about the condition of the engine. Without professional input, you'll be able to tell when something is wrong with your car and take it to the mechanic shop for fixing. The crankshaft has one too.

Symptoms of a faulty camshaft position sensor

 faulty camshaft position sensor

Over time, the camshaft sensor can start to fail or become worn due to accidents or normal wear and tear. If it persists, it could cause your engine to shut down, requiring a rebuild or even a new one. To avoid this, there are signs you can watch out for.They include the following:

  •       Rough engine idling
  •       The vehicle won't come on
  •       Check Engine Light will come on
  •       Poor acceleration
  •       Transmission problem
  •       Poor fuel economy

Key takeaways

The camshaft is an important component of a car's engine due to its role as a valve controller. It must function well at every point in time. If the sensor relays through your car's ECM that anything is wrong, take it to a mechanic shop to get it looked at as soon as possible.

Delay could be dangerous for your engine, leaving you with the option of rebuilding, if you're lucky. You may need to buy a new engine if the damage is severe.

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