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Here are my specs for an aftermarket rocker arm:
Use precision cast steel for strength, reduced weight and long service life.
Explore state-of-the-art foundry techniques (e.g. counter-gravity casting) to reduce costs (pouring, machining, waste) while increasing material strength. However, this might be an OEM process due to initial setup expenses.
Use ti roller and axle on the valve tip end. Roller creates less side load on the valve stem/valve guide; reduces friction at the rocker shaft. Ti reduces weight
Keep friction foot on the cam lobe end and move the adjuster to the cam lobe end. This will be an engineering challenge, but the correct design will produce an adjustable as well as a replaceable friction foot. The adjuster screw, jam nut and roller can also be titanium to save weight. At a minimum, the jam nut can be aluminum or ti.
Make the rocker arm sillouette slim, including the ends. Narrow cross section results in less weight. Use spacers/shims to adjust side clearance and side-to-side alignment.
Use bronze bushing. Needle bearings provide less friction, but bronze bushings have a longer service life.
Provide a slightly higher rocker arm geometry for increased lift.
Provide an oil "well" to ensure adequate lube flow to bushing.
Position of the friction ends of the rocker relative to the center line of the rocker pivot shaft can result in a variable ratio lift, providing a faster opening valve w/o changing the shape of the cam lobe.
Explore relationship of factory mounting point of rocker shaft to valve tip and cam lobe. This area may provide optimization of the rocker geometry.
Roller rocker arms aren't reserved just for high lift cams. OEM's use them to reduce friction which results in better mileage and longer service life.
Sherwood
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