AS9120B, ISO 9001:2015, and FAA 0056B Accredited

What are Valve Train components?

Valve train components are often present within the mechanical systems of a diesel engine or other similar apparatus, serving to manage the operations of intake and exhaust valves. By controlling the intake valves, the fuel-and-air mixture that is being combusted can be governed, while the exhaust valves serve to expel spent gasses from the combustion chamber. Despite being somewhat simplistic in their role, valve train components are essential for the proper functionality of an automobile, aircraft, or other vehicle type harnessing a combustion engine.

Depending on the application and engine, a valve train assembly may feature a number of component types that are present in varying quantities and configurations. Camshaft components are typically found in such systems, featuring a long shaft that passes through the engine head or block. With the egg-shaped lobes present on the camshaft profile, valves can be opened as necessary for air intake. As the camshafts rotate, cam follower bearings follow alongside the lobe so that a low-resistance surface is provided for lift.

Push rod parts, or pushrods, are not always used in a diesel engine. However, they will always be paired alongside a cam when it is in the block, rather than overhead. Push rods are used in unison with camshaft followers to manage the positioning of rocker arms, and to direct oil to the cylinder head. Meanwhile, rocker arms are a form of pivoting lever that pushes against the valve stem when force is applied to them by a push rod or cam follower. If an overhead cam engine is used, the cam follower will be a built-in element of the rocker arm. For the rocker arm to pivot as needed for standard operations, rocker arms are installed onto rocker shaft components.

The valves are another major aspect of valve train systems, and each valve will consist of a head and stem. The head serves as the point of entry and exit for cylinder air, while the stem is the component that force is applied to. To maintain the positioning of the valve, grooves will be present on the stem. Depending on the type of engine that one is using, the number of valves per cylinder may be two or four. As multiple valves will often be actuated at one time during engine functionality, valve bridge or yoke assemblies are used so that a single rocker can manage more than one valve. Once the valve is actuated and the pushrod or rocker arm moves away from the stem, a valve spring will force the valve closed so that it may return to a resting state.

While the rotating camshafts will ensure proper operations, the timing of their movement is also crucial. Generally, a timing belt may be used, its inner side featuring square teeth that mitigate the chance of slipping. A belt tensioner is also important for maintaining tension and alignment with the cam sprocket, and the tensioner comes in the form of a spring-loaded wheel. If the belt needs to be removed for any reason, the tensioner is pulled away from the assembly.

Whether you require fuel injectors, camshaft components, automobile products, or aviation parts, Purchasing Union has you covered with our unrivaled database. Purchasing Union is a website owned and operated by ASAP Semiconductor, and we are a leading distributor of aircraft parts, electronic components, IT hardware, and much more. With new part types regularly added to our catalogs, we invite you to explore our offerings at your leisure. Once you have narrowed down a particular item of interest, use our RFQ service to request a quote for your comparisons and receive a response in just 15 minutes or less.


December 9, 2022
September 23, 2022

Recent Twitter Posts

Semiconductor's Certifications and Memberships
The only independent
distributor with a
  • All parts are stocked in the USA.
  • All parts are shipped from the USA.
  • All shipments must comply with U.S.A export laws.
  • No exceptions.
fallen heroes fund logo

“We Proudly Support Intrepid Fallen Heroes Fund that serves United States Military Personal experiencing the Invisible Wounds of War : Traumatic Brain Injury (TBI) and Post Traumatic Stress (PTS). Please visit website ( and help in their valiant effort”.

Thank You for Visiting Purchasing Union.

Don’t forget That If You’d Ever Like a Quote for Parts Within 15 Minutes or Less, You Can Fill out the Instant RFQ form On this Website’S Homepage.

Request for Quote

We use cookies to ensure that we give you the best experience on our website. If you continue to use this site we will assume that you are happy with it.