In an internal combustion engine, the rocker arm is a mechanical device that transmits the movement of the pushrod to the appropriate exhaust and intake valves.
Engraved steel or aluminum (for high-speed applications) is most commonly used in rocker arm construction. Some types of rocker arms have bearings built into the contact points to reduce friction and wear at the contact points.
The rocker arm is typically located between the intake valve and the exhaust valve and pushrod. This pushrod is used to push and pull the arm. This pushing action of the pushrod “rocks” the rocker arm up and down. For this reason, the intake and exhaust valves of the engine combustion chamber, which has a camshaft under the engine, are opened and closed.
The camshaft is connected to the crankshaft. The camshaft is powered by the crankshaft. When the camshaft receives movement from the crankshaft, the pushrod moves up and down. The push rod also transmits its movement to the exhaust and intake valves via the rocker arm.
Proper opening and closing of the exhaust and intake valves ensures proper fuel supply to the engine. Ultimately, the fuel burns in the combustion chamber to produce electricity. This generated energy is transmitted to various parts of the engine that propel the vehicle.
If the rocker arm is cracked or loose, the exhaust and intake valves will not function properly and the cylinder associated with the damaged rocker arm will be disabled. This has a great impact on engine performance.
Table of Contents
How Does Rocker Arm work?
The rocker arm is part of the engine and provides the engine with the proper fuel. One end of the rocker arm is connected to the pushrod.
When the crankshaft rotates, that rotation is transmitted to the camshaft. When the camshaft is powered, the push rod is pushed up. The top of the pushrod pushes on the side of the rocker arm to rotate the arm. This rotation pushes the other end of the rocker arm down onto the top of the valve, causing the valve to move down and open.
When the outside of the valve returns due to the rotation of the camshaft, the inside rises and the valve closes.
Rocker Ratio?
The rocker arm ratio is the ratio of the amount of movement that the valve moves to the amount of effective movement that the pushrod moves.
The rocker ratio can be calculated from the ratio of the distance between the point connecting the rocker arm pivot to the camshaft and the point connecting to the valve contact point. If the rocker ratio is greater than 1, the camshaft lift will increase significantly.
Types of Rocker Arms
In general 4 types of rocker arms are used: 1. Stamped steel rocker arm, 2. Roller tipped rocker arm, 3. Full roller rocker arm, 4. Shaft rocker arm.
Let’s talk about these 4 types of rocker arms in detail.
1. Stamped steel rocker arm
This is one of the most well-known types of rocker arms. These rocker arms are punched out of a single piece of metal, resulting in a simple design. They are cheaper than other rocker arms.
The engraved steel rocker arm uses a pivot pin with a round bottom nut that holds the rocker arm in place. This is a simple and easy way to rotate the seesaw up and down and keep it in place.
2. Roller tipped rocker arm
These rocker arms are very similar to the engraved steel rocker arms. A roller is attached to the tip of the rocker valve. This design reduces friction, reduces valve tip wear, and improves power output.
For convenience, this rocker arm contains pivot bolts and nuts. They are made of cast or machined aluminum or steel.
3. Full roller rocker arm
It is not an engraved steel seesaw. It is made by machining aluminum and steel. Bearings are included instead of pivots.
The full roll seesaw can also use bolts for the pivot, but not nuts. Includes a short shaft. This shaft contains bearings on both sides. The shaft is firmly bolted and the bearings rotate the rocker arm.
4. Shaft rocker arm
It comprises a full roller rocker arm. Comes with a shaft that penetrates the rocker arm. Depending on the cylinder head design, the shaft can only pass through two rockers or all rockers. This shaft is used because of its high rigidity.
The stiffer the valve train, the less deflection it has and the less likely it is that the valve train will move at high speeds and become uncontrollable.
Signs of Bad Rocker Arm
- Click or tick sound
- Fire or stall
- Reduced performance
- Check that the engine light is on
- Physical deterioration