Guide to Rocker Arms

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Guide to Rocker Arms

The rocker arms inside an internal combustion engine are more than just a simple mechanical component. They are essential in the operation of the valve train and incredibly vulnerable to wear and breakage overtime. Therefore, taking care of rocker arms, which includes upgrading their quality and replacing them as needed, is essential. It is important for car owners and mechanics to first understand the importance of these components, as well as the many options they have when buying new ones.


The importance of rocker arms

The basic function of rocker arms is relatively straightforward. However, their position and role inside an internal combustion engine sets them up as powerful components in terms of not only proper engine operation, but also overall power.

How rocker arms work

Rocker arms work as oscillating levers, which transfer the radial movement of the cam lobe into a linear movement in order to open the poppet valve. This exchange is a literal "turning point", which is critical to the operation of the engine. However, the transfer of energy taking place, known as deflection, subjects the rocker arms to stress and increased vibration, particularly as a vehicle reaches high speeds. Over time, the metal of the rocker arms fatigues, causing wear and friction in the valve train. If left unattended, this can cause complete engine failure.

Increasing engine power

While the basic function of rocker arms is essential to normal engine operation, enhanced function can positively affect engine performance and power as the arms better tolerate the stress of high-speed engine operation. By upgrading rocker arm quality, drivers can increase engine efficiency and power in three main ways:

  • Increasing valve lift
  • Stiffening the rocker arms
  • Decreasing the rocker arm's resistance, or moment of inertia

Therefore, by paying attention to the type of rocker arms an engine uses and their relative ratio, stiffness, and resistance to rotation, drivers positively impact the performance of their vehicle.


Types of rocker arms

When it comes to improving engine performance through rocker arm upgrades, owners should consider the type of rocker arms they want to use. There are several options that work in either push rod or overhead cam engines.

Stamped steel

The most basic type of rocker arm used in a push rod engine, stamped steel rocker arms are made of a single piece of steel. A trunnion pivot holds each arm in its position, which is secured with a rounded nut. The nut secures the rocker while allowing the entire unit to pivot up and down.

Full roller

Made of either machined steel or aluminium, full roller rocker arms are for push rod engines and use bearings rather than a trunnion pivot to hold the rocker in position. Full roller rocker arm shafts are short and bolted into place, which allows the bearing part of each arm to pivot.

Roller tipped

Similar in structure to a stamped steel rocker arm, a roller tipped rocker arm is also used in push rod engines. As the name suggests, these rockers include a roller tip at the valve end of each arm. Made of aluminium, cast, or machine steel, the roller tip rocker arm uses the same trunnion pivot and bolt construction as the stamped steel rocker arm.


The last option for push rod engines, shaft rocker arms are similar to full roller rocker arms, utilising a bolted shaft that runs through two or more arms. The shaft provides increased rigidity, helping to improve performance by making the rocker arm stiffer and less prone to deflection and fatigue.

Centre pivot

One of two options for overhead camshaft engines, the centre pivot rocker arm may look like a traditional push rod rocker arm, but there is one big difference. The centre pivot rocker arm does not push the pushrod into the lifter, but rather pushes the camshaft into the lifter to force the poppet valve down. As its name suggests, the pivot point of this rocker arm lies in its centre.


How to buy rocker arms on eBay

Shopping on eBay to find the right rocker arms for your vehicle is a fast and easy way to make this critical upgrade or repair. Simply start a search from any page of the site using the main search bar. Enter a general term, such as "Nissan rocker arms", or be more specific as to type or brand within the query. It is easy to narrow search results using the filters provided, which include aspects such as price, condition, and location of the rocker arms.

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