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Roller Rocker Arms

 COMP® ROCKER TECH

 

One of the most important components in your engine is the rocker arm. It is also one of the most vulnerable. As the turning point of the valve train, the rocker arm is basically a sophisticated lever that redirects the upward tappet and pushrod movement and then multiplies it by the rocker ratio to downward movement at the valve. This is a highly critical process. Due to stresses and vibrations, which are more prevalent during high speed operation, rocker arms undergo what is known as deflection. Severe rocker arm deflection causes inefficient engine performance, and often results in metal fatigue leading to increased wear and friction in the valve train and eventually engine failure.

SOME BASIC WAYS TO INCREASE POWER THROUGH ROCKER CHANGE

INCREASE VALVE LIFT By increasing rocker ratio, it’s possible to increase valve lift without ever touching the camshaft. Lift can typically be increased as much as 10%.

INCREASE ROCKER STIFFNESS To increase rocker stiffness, look at three characteristics: material, geometry and the rocker’s holding fixture. The easiest way to increase stiffness is to switch to chromemoly steel. Although heavier than some other materials, it can offer some design advantages and have much thinner sections than aluminum due to its superior strength density. Stiffness of the mounting is just as important as the stiffness of the rocker body. For the ultimate in high performance, shaft mounted rockers may be the way to go.

DECREASE MOMENT OF INERTIA The moment of inertia (M.O.I.) is the rocker’s resistance to rotation. The higher this measurement, the more valve spring pressure it takes to control the rocker arm instead of the valves – losing RPM and horsepower. The M.O.I. is lowered by lightening the rocker arm’s weight, particularly at areas that are farther from the trunnion. Two ways you can do this are by switching to a lighter weight material or by removing mass from the rocker body.

 ALUMINUM ROCKERS  Until recently, aluminum rocker arms have been considered a more affordable but less durable option to steel rockers. This is because when directly compared to steel, aluminum requires more material to handle the stress of a given force. Since more material is required and there is a limited amount of space available in the trunnion, the bearing and axle are typically smaller in an aluminum rocker arm. Previous designs weren’t able to be used in extreme applications and featured decreased stiffness and increased deflection. But COMP Cams® has developed aluminum rockers that use precision-sorted needle bearing trunnions to withstand both aggressive spring pressures and valve lift. The COMP® Ultra-Gold™ ARC Aluminum Roller Rockers actually have the highest rocker-to-valve spring clearance of any aluminum rocker – up to 1.625" valve spring O.D. And while these aluminum rockers are lightweight, they are still incredibly strong and feature a lifetime warranty.

 CHROMEMOLY STEEL ROCKERS  COMP Cams® steel rocker arms are all constructed from 8620 or 8650 chromemoly steel, which is a higher grade material that makes them extremely durable and tough. The material keeps them from flexing, and they have large trunnions and more needle bearings, which allow the load to be more evenly spread and the rocker to last longer. Steel can thus be run in harsh environments without fatigue issues. And some COMP® steel rockers are even lighter than most aluminum because COMP® has reduced mass in low stress areas.

 STUD & SHAFT MOUNTED ROCKERS   Rocker design continues to evolve as more aggressive cam profiles and cylinder heads are developed. Stud mounted rockers have evolved over the years. Starting as a simple ball-and-socket mounted stamped steel piece, the first modification was to change the mount to a roller bearing and a transverse mounting axle. Next, larger screw-in studs were added. Soon, geometric designs had to change and stiffer material was required, giving way to the innovative arched web design as seen in today’s Ultra Pro Magnum™ and Ultra Pro Magnum™ XD Rockers from COMP Cams®.

The next step in rocker arm technology is the shaft mounted rocker. Rather than being mounted on a stud, a horizontal shaft works as the fulcrum. This significantly increases the mounting stiffness and valve train stability. Shaft mounted systems are designed for highend performance applications. A cost-effective alternative is to use a stud girdle to reduce deflection with stud mounted rockers.

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  1. Ultra Pro Magnum™ • Small Block Chevy • 3/8" Stud • 1.52 Ratio
  2. Ultra Pro Magnum™ Roller Rocker Arms
  3. Ultra Pro Magnum™ Roller Rocker Arms
  4. Ultra Pro Magnum™ Roller Rocker Arms
  5. Ultra Pro Magnum™ Roller Rocker Arms
  6. Ultra Pro Magnum™ Roller Rocker Arms
  7. Ultra Pro Magnum™ Roller Rocker Arms
  8. Ultra Pro Magnum™ Roller Rocker Arms
  9. Ultra Pro Magnum™ • Ford Small Block 289-302-351W • 3/8" Stud • 1.6 Ratio
  10. Ultra Pro Magnum™ • Ford Small Block 289-302-351W • 7/16" Stud • 1.6 Ratio

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