A valve lifter, which is also called a tappet or cam follower, is a small cylinder-shaped part of an engine’s valvetrain. Depending on the type of engine, it sits either between the camshaft and the pushrod or right on the camshaft. The valve lifter’s main job is to turn the camshaft’s rotational motion into linear motion. This makes the intake and exhaust valves of the engine open and close.

This blog, available on the KSB Autostyling website, briefly introduces you to the valve lifters, their working and their importance. A comparison is also made between its different types to guide you about the benefits associated with each one.

Valve Lifter: Then

The history of valve lifters dates back to the earliest times of the internal combustion engine. In the earliest days, there were no pushrods, and they employed a flathead design with valves situated beneath the combustion chamber. Lifters rode on the lobes inside the engine block and operated the valves. 

Valve Lifter: Now

The transition to the overhead–valve engine marked a significant advancement, allowing the engine to work efficiently and produce more power from the same size. However, this advancement created trouble for the valve train, so it became necessary to include pushrods and rocker arms. Moreover, the lifters also had to facilitate the oil flow up to lubricate upper valve train components.

Role of Valve Lifter

The fundamental role of a valve lifter is straightforward. Positioned on the camshaft, it transfers the motion of the cam lobe to open and close valves through the pushrods and rockers. The size and the shape of the cam lobe determine valve lift and duration. The lifters follow the motion of the cam lobe. It also plays a role in valve train lash and contributes to noise management within the engine. 

How does the Valve Lifter Work?

The camshaft has various egg-shaped cam lobes on it. There are mainly two valves in pushrod engines and 16 lobes on the camshaft. The lower end of each valve lifter sits on a cam lobe. With the camshafts spinning, the cam lobes move, causing the lifters to move up and down. The top end of each pushrod positioned on a lifter pushes upward on a rocker’s arm. As the pushrods push upward on the rocker’s arm, its other end moves downward at the top of the valve stem, leading to the valve’s opening in a downward direction. 

Each cylinder usually has two valve stems: the exhaust valve stem that releases the air mixture from the combustion chamber and the intake valve stem that brings the air into the chamber. Simply put, a valve lifter transfers the motion of the cam lobes to the rocker arm/ pushrods to open and close the valve. They are crafted in very specific dimensions and are neither too long nor too short. Their correct size is very important for the opening and closing of the valve lifter.

Mechanical vs. Hydraulic Valve Lifters

Solid lifters or mechanical valve lifters are made up of metal in specified dimensions. As they wear over time, the valve train is adjusted to accommodate and run the engine smoothly. This adjustment is required to be done frequently. Hydraulic valve lifters have oil filled in them when the engine is running. They adjust themselves when they wear. The longevity of the hydraulic lifter is quite impressive, and it lasts over a refined engine up to 100k miles. To summarise their comparison, we can say,

• Hydraulic lifters minimise valve train noise and disturbing vibrations. The noise reduction is done by maintaining a clear area between the stem and pushrods. Thus, you can enjoy a smooth and noise-free ride on your vehicle.

• Hydraulic valve lifters adjust themselves when they wear or due to thermal expansion. This frees you from the manual adjustment required in the case of mechanical lifters, thus simplifying the maintenance of the engine and reducing the risk of wrong adjustment. 

• Consistent valve timing and life provided by hydraulic lifters enhance the engine’s performance, manifested by higher output and increased efficiency. 

• Mechanical lifters also have certain benefits, like they are cheaper and low-maintenance. They work perfectly for performance cars.

Summarising the Importance

The valve lifters control the combustion process by letting fuel in and exhaust from the chamber. When the valve lifters wear, they cannot work for the opening and closing of valves; hence, the engine does not work efficiently. They are the most essential parts of the combustion engine. 

Visit KSB Autostyling for all your basic car needs. We have high-quality essentials for your favourite vehicle.

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