Here is part of an article from CHP with a Q & A with Brad Rounds of T & D machine
Roller Rockers Steel Or Aluminum?
Brad Rounds: "There is certainly a tradeoff in strength and durability between aluminum and steel rockers. The vast majority of rockers we manufacture are aluminum, but the NASCAR teams we work with demand the durability of steel. Generally, aluminum rockers are lighter, easier to manufacture, and provide a dampening effect on the valvetrain. However, all aluminum rockers have a finite cycle life. On the other hand, steel rockers are more durable and provide a slight increase in cycle life over aluminum. The tradeoff is that they're heavier, harder on other valvetrain components, and more difficult to manufacture. Although much of what T&D builds for top racing series like NASCAR Sprint Cup is proprietary, and therefore somewhat secret, it can be stated that there has been a strong exodus from aluminum to billet steel in rocker body construction. The reason is quite simple: A rocker arm must last through the high-rpm, fully orchestrated chaos that is now the NASCAR norm.
"Through years of development and testing, we found the absolute limit of aluminum rocker arms. Some of our customers wanted a rocker that had longer cycle life with higher ratios, and the answer was steel. For us, the progression to steel was actually a natural one. The initial customer for T&D steel rockers was Mercury Marine, a company that uses T&D as an OEM product on many of its offshore powerplants, even in non-race applications. Once the piece was engineered, it did not take long for others to ask for steel. The initial steel offerings were not just an aluminum design milled out of steel. They were designed as steel rockers from the ground up. The current NASCAR Cup rockers have evolved light-years from those initial attempts, not only in design but in material as well. Our proprietary manufacturing process ensures both strength and ductility for maximum reliability. Outside of NASCAR, steel rockers have become very common in blown and nitrous applications, tractor pullers, dirt late-models, and sprint cars."
Roller Rockers Steel Or Aluminum?
Brad Rounds: "There is certainly a tradeoff in strength and durability between aluminum and steel rockers. The vast majority of rockers we manufacture are aluminum, but the NASCAR teams we work with demand the durability of steel. Generally, aluminum rockers are lighter, easier to manufacture, and provide a dampening effect on the valvetrain. However, all aluminum rockers have a finite cycle life. On the other hand, steel rockers are more durable and provide a slight increase in cycle life over aluminum. The tradeoff is that they're heavier, harder on other valvetrain components, and more difficult to manufacture. Although much of what T&D builds for top racing series like NASCAR Sprint Cup is proprietary, and therefore somewhat secret, it can be stated that there has been a strong exodus from aluminum to billet steel in rocker body construction. The reason is quite simple: A rocker arm must last through the high-rpm, fully orchestrated chaos that is now the NASCAR norm.
"Through years of development and testing, we found the absolute limit of aluminum rocker arms. Some of our customers wanted a rocker that had longer cycle life with higher ratios, and the answer was steel. For us, the progression to steel was actually a natural one. The initial customer for T&D steel rockers was Mercury Marine, a company that uses T&D as an OEM product on many of its offshore powerplants, even in non-race applications. Once the piece was engineered, it did not take long for others to ask for steel. The initial steel offerings were not just an aluminum design milled out of steel. They were designed as steel rockers from the ground up. The current NASCAR Cup rockers have evolved light-years from those initial attempts, not only in design but in material as well. Our proprietary manufacturing process ensures both strength and ductility for maximum reliability. Outside of NASCAR, steel rockers have become very common in blown and nitrous applications, tractor pullers, dirt late-models, and sprint cars."
