You engine's rocker arm keeps your engine's valves opening, at exactly the right moment, like clockwork. It makes sure that your engine is up to its optimized speed and rhythm, or if it fails, your engine conks out. Since rocker arms are fairly standard in their design, here are some things that can help you when buying a new set of rocker arms.
In most things in and on the car, lighter is usually better. Of the two, aluminum is the lighter and, often, the more affordable choice. It you want to save a little, you go for an aluminum rocker arm. That is not to say that aluminum arms are weak-they are still effective in their own right and are generally smaller. It's just that they are not that durable.
That is not to say that they're simply break down more quickly; you just have to keep a close eye on them. You may ask, why not make all rocker arms out of stronger steel? It's because aluminum rockers are durable enough for city-commuter driving.
Since it was used in a lot of industrial applications, steel is the metal of choice for those who are looking for strength and durability. It might not be as flexible as aluminum, but it certainly lasts longer when put up to the continuous motion that it has to undergo. The only real drawback of steel is that rocker arms cost much more than their lighter aluminum equivalents.
The Perfect Fit
When you have decided which of the materials you prefer, you still might want to check out whether the replacement you are looking for is a perfect match for your ride. Pictures in a catalog and in a store can be deceptive-rocker arms may be sized differently, but they look the same. It helps to keep the original rocker arm with you as you shop.