The best push rods to use is 4130 chrome moly that has been case hardened. Chromemoly tubing has high resistance to bending and can be case hardened for a high resistance to wear. Factory and Comp Cams High Energy push rods are hardened by carburizing (heat treated) and are made of plain mild steel. Mild steel push rods can fold up like spaghetti with spring loads over 300 lb.
To save a few pennies, GM increased the diameter of their mild steel push rods in some of their high performance engines in order to resist bending. Larger diameter push rods are heavier, especially when they are filled with oil.
Comp Cams High Tech series are made of light weight SAE 4130, 5/16" OD, chromemoly .080" wall tubing and are case hardened for use with guide plates. Those are excellent quality push rods and should be considered with spring loads from 300 to 400 lb.
Last edited by MouseFink; 01-26-2013 at 08:56 AM.