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1. Why is steel better than aluminum as a material for rocker arms?
Aluminum, unlike steel, has no safe stress point. With aluminum, every cycle endured is one cycle closer to failure. To make things worse, the failure point of aluminum is very unpredictable. The advantage of high quality steel is that as long as it cycles at less than its maximum failure point, it can be run for virtually a lifetime without failure. Steel just doesn’t have the same cycle failure problem that aluminum has.
2. Can roller rocker arms be rebuilt?
Most roller rocker arms are not rebuildable, -with two notable exceptions being the Pro Magnum™ and Hi-Tech™ series from COMP Cams®. These 8650 chromemoly steel (stainless steel for the Hi-Tech™ series) rocker arms carry a lifetime guarantee on the rocker bodies, and if needed, can be rebuilt in-house at COMP Cams®. During this process, the rocker bodies are disassembled and inspected, and all moving parts such as the roller tip, axle, trunion, and bearings are replaced. Essentially you receive a new set of rockers for a fraction of the cost.
3. Can I run stock, non-adjustable rocker arms with an aftermarket camshaft?
Simply put, factory rocker arms are for factory camshafts. Factory rockers aren’t designed to handle the lift and duration of a performance camshaft. Non-adjustable rockers also do not allow correction of the rocker arm geometry or lifter preload, which are critical to engine performance and reliability.
4. How much power can I expect to gain when I replace my stock rockers with full roller rockers of the same ratio?
Typically when you replace a factory rocker arm you will see an average gain of 15HP. When considering the speed at which your valve train is moving at 6000 rpm, any reduction in friction and heat will obviously promote more power and less wear. One more benefit of an aftermarket rocker arm such as the Pro Magnum™ series is the super accurate rocker ratio. factory mass production techniques.
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A full roller rocker design, such as the Pro Magnum™ series, incorporates a roller tip and roller trunion bearing to reduce the internal heat that is created at the valve and fulcrum. Combine these features with an ultra-strong 8650 chromemoly steel body and it’s easy to see how advanced a set of COMP Cams® rocker arms are compared to the factory units.
5. Does switching to a higher rocker ratio
increase performance?
Increasing rocker ratio results in a “larger” camshaft profile based on more valve lift and faster opening and closing of the valves, which can mean an increase in performance. As an example, to determine the change in cam specs made by switching from a 1.5 ratio to a 1.6 ratio we need to calculate as follows:
Assuming a .500” lift camshaft (with a 1.5 ratio); we will first need to calculate camshaft lobe lift. The lobe lift calculation is:
Valve lift/Rocker Ratio (current) = Lobe Lift
Plugging in the numbers for our current cam and rocker ratio gives us .500/1.5, which equals .333” of lobe lift. Rearranging the equation gives us the means of figuring our gross valve lift with the new rocker ratio:
Lobe Lift X Rocker Ratio (new) = Valve Lift
Inserting the lobe lift specs for our cam and prospective rockers gives us .333 X 1.6, which equals .534” –a substantial difference in lift. Note that a lot of people assume that switching to a 1.6 from a 1.5 gives .030” more lift, or some other number –this is true in some cases, but as this change represents a ratio, not a constant, it is unwise to assume that the lift increase will be any set number –do the math, and you’ll never have to guess !
Also, remember that if you are running a split pattern cam with a difference in lift between the intake and exhaust lobes, you’ll want to do the equation twice (once for each lobe) in order to accurately calculate your gross valve lift. And last but not least, when swapping to a higher rocker arm ratio, you must verify that you have enough piston-to-valve and coil bind clearance to accommodate the increased lift, or disaster could result.
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