Rocker Arm

Author

Javaughn Barrow

What you will learn :

What Are Rocker Arms?

Rocker arms are mechanical components in the form of pivots in an engine that aid in opening the intake and exhaust valves. They transfer rotational forces from the cam to the intake and exhaust valves. It does so by influencing the opening stages of the valve operation. The design of cam lobes makes it so that it pushes the positions of a rocker arm in one direction. Rocker arms are designed like a rocking seesaw (pivot) that moves one end up while the opposing side moves down. This motion is integral in valve operation because it allows the rocker arm to receive motion from one end, while the opposite side pivots in the opposite direction. As a result, these forces push open the intake and exhaust valves. The section of the rocker arm that pivots down is the section that moves on the valve stems thus opening the pathway for intake air or exhaust flow.

Rocker Arm Engine Types

• Push Rod Engines:

Push rod engines are a particular type of design engine where the cam sits below and/or between the engine headers. Because of its positioning, it uses an extension called push rods to push up on the rocker arms which then intern pushes open the intake and exhaust valves.

Common materials used for rocker arms are stamped steel and aluminum. These materials bring benefits in terms of being lightweight and strong. Those two qualities alone do a lot for the stability of the overall valve train. 

• Overhead Cam (OHC) Engines:

Overhead cam engines are engines that are designed with the camshafts in the headers. This is the top section of the engine. This positioning allows for more direct contact with the intake and exhaust valves. Not all OHC engines use rocker arms. Single Overhead Cam engine engines (SOHC) use rocker arms, while Dual overhead Cam engines either use tappets or end pivot rocker arms. SOHC engines have the rocker arm fulcrum (pivot) in the middle. The use of a single camshaft uses middle pivot rocker arms to transfer the rotational force onto the intake and exhaust valves. 

Common Types of Rocker Arms

• Stamped Steel Rocker Arms: These are your commonly used, basic, and cost-effective rocker arms

• Roller-Tipped Rocker Arms: These are rocker arms with roller tips. The section of the rocker arm that makes contact with the section of the valve springs is designed with rollers that rotate when there is an up or down motion. This design improves performance while reducing friction, both go hand in hand.

• Full Roller Rocker Arms: Full roller rocker arms are designed with a roller at the pivot point of the rocker and a roller tip. This design is a premium option for high-performance engines.

• Shaft Rocker Arms: Shaft rocker Arms are high-performance full roller rocker arms mounted on a shaft that is specifically designed for heavy-duty and high-performance racing applications. 

Rocker Ratio

Rocker ratios are ratios used to multiply the camshaft lobe lift by. Camshaft lobe lift is how much the surface has raised from the circumference of the camshaft. How much the surface is raised is multiplied by the ratio of the rocker arm which gives you how many more times the valve opens. This gives you an accurate depiction of how much the valves extend into the combustion chamber to allow air/fuel intake or exhaust. The more valve lift there is the more volume of air or exhaust can pass through, which has a relative impact on the performance of the engine. 

Applications and Modern Considerations

When selecting or understanding rocker arms, knowing the type of engine is a good place to start. OHC and OHV (pushrod) engines use different rocker arms simply because each engine is meant for different applications. Some may not even use rocker arms. The fulcrum/pivot in a rocker arm changes its application in an engine. Rocker arms come with pivots at the end and in the middle. For some dual OHC engines end pivot rocker arms are used while in pushrod and single OHC engines middle pivot rocker arms are used. Companies will use software programs like AutoCAD, Stillworks, etc, to account for the details of rocker arm design. Each design matches with engine application and performance to produce the best possible result in engine performance. 

FAQ

1. What is the function of a rocker arm in an engine?

A rocker arm transfers the rotational force from the camshafts to the intake and exhaust valves causing them to open for combustion to take place.

2. What are the symptoms of a bad rocker arm?

Rocker arms are key in engine performance. In the case of defective or worn rocker arms aside from clicking and ticking noises from the engine, you should also experience misfires, reduced engine performance, and a check engine light. Check engine light codes for faulty rocker arms are P2645 or P2646.

3. How much does it cost to replace a rocker arm?

Rocker arms are typically located at the top of an engine and typically cost anywhere from $100 – $500 to replace.

4. Can you drive with a broken rocker arm?

Broken rocker arms usually come with engine misfires and reduced performance. Not only is it not safe to drive a car in this condition it is not advisable as it can cause further more extensive damage.

5. What causes rocker arms to fail?

Other than wear and tear, lack of lubrication can cause rocker arms to become faulty. Rocker arms make metal-to-metal contact so proper lubrication is key for operation. Other causes are improper adjustments or manufacturing defects. 

Javaughn Barrow

Hello! My name is Javaughn Barrow, a young car enthusiast who writes all the articles for Karcandy.com. I’ve written over 50 articles about automobiles. With each article, I deepen my understanding and expertise in writing and the automotive world. Ever since childhood, I’ve always had a strong passion for cars. All types shapes and sizes were interesting to me. I’d spend most of my time after school researching cars and the more I found out about them the more exciting it was. In my teens, I created a fan page about corvettes posting content at least ten times a day! Yes, I was crazy about it. The page ended up garnering over 40k followers! After a while, I wanted more than a fan page. I wanted to express my passion differently. I wanted to create more helpful content, higher-quality content. My first car was a 2013 VW CC Sport. Learned very quickly car ownership wasn’t as expected. I spent a lot of time replacing control arms, cam position sensors, brake rotors, brake pads, etc. Walking away with more information than I knew before. As I was growing in my automotive journey I was learning about writing. Starting by writing a detailed outline about 300 words long then I would pay a professional to write a full 1000-word article and learn from them getting familiar with the process of writing. The moment I realized I could use my writing skills to express my passion for cars and help people simultaneously, I started Karcandy.com. I realized with my unique perspective coupled with my hard work discipline and work ethic I can create a space online to help bridge the gap between the complicated and simple in the automotive world. I’m motivated by the challenges and work it will take to create such a space. My work ethic is something I choose to refine and make better each day. I think it’s important to push myself and stay committed to my evolution as a human and this website is only one of the results of that.

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