The rocker arm is possibly the third most abused part in your engine. The connecting rods take the cake for the most abuse, followed closely by the piston assembly, but we like to think the rocker arms get the bronze for beatings when you’re goosing the throttle in your V-8 of choice.
When it comes to building a performance engine, rockers can do more than simply transfer the motion of the pushrod; rocker arms can change rpm limits, rpm acceleration, and they can even alter your camshaft’s overall behavior. Although simple in theory, rockers are actually far from simple in the high-performance and racing world. In a stock engine, we imagine the rockers live a boring life; basically just transitioning the movement of the pushrod, easily pushing down the low-pressure single coil valvesprings until the cows come home. But as your desire for horsepower increases, the durability and construction of the rockers you choose has to improve as well if you want the most from your engine combo.
Choosing the right rocker isn’t the only thing to keep in mind, you also have to install them correctly, and sometimes, if you don’t know what to look for, it can be tricky. As we change camshaft profiles, valvespring heights, and mill and deck our engine blocks and heads, those all factor into getting the rockers to fit properly and valvetrain fitment is crucial for a long-lasting engine combination.
According to COMP Cams, there are three ways to improve your engine’s power output through a rocker arm change: Use a higher ratio rocker arm to increase overall cam lift and duration, make the rocker body stiffer so no lift is lost by flex, or lower the weight of the rocker so it can accelerate quicker. Increasing the rocker ratio is a way to trick your camshaft into thinking it’s bigger than it actually is. By manufacturing rocker bodies with various arm lengths, this increases the ratio, thus increasing the final lift and duration at the valve. This is oftentimes what gearheads do if they need more cam but don’t want to pull the engine apart. As valvespring pressures increase, rocker body stiffness plays a huge factor in getting the most from your rockers. For years, the engines in the NASCAR circuit used aluminum rockers, but relatively recently engineers have figured out that the amount of flex coming from pushing on super-stout valvesprings was reducing the overall lift of their camshaft, which prompted all the NASCAR teams to switch to lightweight, yet low deflection rockers so they could get every fraction of cam lift from their profile. Reduced rocker body mass is another way companies have improved rocker arm performance over the years. The more rpm your engine experiences, the more valvetrain mass becomes important. For a low-rpm engine, rocker weight/mass is not crucial, but on an 8,000- to 10,000-rpm screamer where the rockers move incredibly quickly, every gram counts.
Read on as we explore how to properly install COMP’s Ultra Pro Magnum stud mount roller rockers as well as give some inside info from COMP Cams and T&D Machine’s engineering department.
For good measure