Rocker Arm Ratio Explained

You've heard of 1.5:1 ratio and 1.6:1 ratio rocker arms. What does that really mean? How can you make more horsepower by using the larger ratio rocker arms?

The ratio of a rocker arm refers to the amount of movement on the valve side of the rocker arm in comparison to the pushrod side. A 1.5:1 rocker arm will move a valve 1.5 times the lift of the cam, assuming all things are in proper working order. If your cam has a lift of .4 inches, multiply by 1.5 to get .6 inches of actual valve movement. With the same cam lift of .4 inches: If you do the math on a set of 1.6:1 rocker arms: Multiply 1.6 x .4 inches of cam lift. You get .64 inches of actual valve movement. Essentially, changing to a larger ratio rocker arm is the same as increasing the lift of your cam the same amount. Opening both valves further usually is a benefit in the power department as your engine is capable of moving more air and exhaust through it.

NOTE: Please be sure your valve springs and valvetrain are capable of handling the additional lift of adding a rocker arm with a larger ratio. Maintaining valve to piston clearance is also critical!