Guide To Rocker Arms

State-of-the-art roller rocker arms solve this problem by using roller bearings instead of the rocker-ball pivot. A roller bearing produces far less friction and heat than the stock rocker's sliding action. Because of this, oil flow to the topside of the engine can be restricted. Not only does this reduce the overall engine oil temperature, it can help produce more usable horsepower.

Rocker Ratios
Check out this example: A small-block Chevy has a stock theoretical ratio of 1.5:1. If that ratio is changed to 1.6:1, then the gross valve-lift numbers increase without affecting the valve-seat timing. In short, the advertised duration stays the same, but the lift is larger.


In addition to lifting the valves higher, a larger-than-stock-ratio rocker also opens the valve quicker and closes the valve slightly later. Naturally, there are some tradeoffs. For one, springs must be checked for coil bind. In addition, the quicker acceleration and deceleration rates produced by high-ratio rockers can produce a certain amount of instability in the valvetrain, which in turn can result in valve float. Fortunately, this instability problem is almost always restricted to maximum-effort, on-the-ragged-edge race engines.


How is the ratio changed in the rocker? When the rocker is designed and constructed, the ratio is increased by moving the pushrod cup closer to the fulcrum or pivot area. The physical differences in the bases are visible in the two Crower big-block Chevy rockers shown in Tip 1.


So which rocker is right for you? There's a rocker arm for every application. Some are low-buck, others are exotic. But in any case, there could be extra horsepower lurking under the valve covers.