Pushrods under load at high engine speed wobble and flex. With high spring pressures, pushrods can deflect and throw off the valve timing, leading to poor valvetrain stability, valve timing, or consistent power and in many cases, lifter failure. Increasing the diameter and wall thickness of the pushrods makes them stronger and stiffer, and more stable. Makes much more sense to have a more stable valvetrain, dont skimp on pushrods.
Reliability & Failures: Many pushrod and lifter wheel failures can be traced back to poor valvetrain stability. Its a must in performance applications to use a High quality, Chromemoly pushrod. Use the largest pushrod diameter possible that still provides the necessary clearance in the cylinder head and rocker body. You can also use a thicker wall pushrod to achieve the needed results. An incorrectly used pushrod is under load, they flex much like a pole vaulter's pole. Which allows the lifter to leave the camshaft lobe in the quick ramps. The lifter is then smacked by the rotating lobe which damages the lifter and failure is imminent. Rocker Arm flex is also a factor in valvetrain stability.
Power: As power becomes flat or decreases due to “valvetrain stability,” the biggest culprit is often the pushrod deflection. In tests conducted by a prominent cam manufacturer, they claim to have found 12 hp on a SBC with a 204/214 @ .050 cam (.420/.443 valve lift) just by going from a .065˝ wall stock pushrod to a .080˝ wall pushrod, and the springs were only 110 lbs. on the seat and 245 lbs. open
Materials: Most OEM pushrods feature low-carbon steel tubes and ends. Some manufactures use a mild performance 1010 Carbon. Total Performance recommends the use of a high quality Chromemoly.
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