Rocker Arm


A rocker arm is an oscillating lever that conveys radial movement from the cam lobe into linear movement at the poppet valve to open it. One end of the rocker arm is raised and lowered by a rotating lobe.

When the camshaft lobe raises the outside of the rocker arm, the inside presses down on the valve stem, opening the valve. There are several parts to a rocker arm:

  • Trunnion pin – projection from lifter
  • Tappet – adjustable blocks
  • Poppet valve – used to control timing

Some overhead cam engines employ short a rocker arm in which the cam lobe pushes down on the rocker arm to open the valve. On this type of rocker arm, the fulcrum is at the end rather than the middle, while the cam acts on the middle of the arm.

Delta Camshaft can answer all of your rocker arm questions.

Roller Rockers


Roller rockers are a rocker arm that uses bearings instead of metal sliding on metal. That is why it is called a roller rocker.It has a wheel on its end like that of a measuring wheel, which rolls by the use of bearings. For pushrod engines, roller rockers employ a roller where the rocker contacts the valve stem.

  • Up to 10% horsepower increase
  • Reduction of friction and wear
  • Increase rocker ratio

Roller rockers can also be used in overhead cam engines. However, these roller rockers generally have the roller at the point where the cam lobe contacts the rocker. Roller rockers help to reduce cam lobe friction and wear in the same way as roller lifters on pushrod engines.

Rocker Arm Replacement


Rocker arm replacement is essential to any engine rebuild. The push rod pushes the rocker arm up and down about the trunnion pin or rocker shaft. Friction causes wear and tear creating the need for rocker arm replacement.

Any time you are rebuilding or replacing a camshaft it is recommended that you consider rocker arm replacement. Rocker arm replacement can assist in getting the full benefits of a new camshaft.

  • Rocker shaft - changes radial movement into linear movement
  • Roller tip – small rolling bearing on end of rocker arm
  • Intake valve - controls the passage of fluid or air into the cylinder

Rocker arm replacement can create more power. It can also reduce the oil temperature of the motor due to the lack of friction being created. Call Delta Camshaft today (800) 562-5500 for rocker arm replacement.