For rods, we are using K1 Technologies H-Beam rods part number 015BX17152. We believe that these are some of the best rods available for the price point. K1 rods are made out of tough 4340 steel forgings. 4340 is a steel alloy high in nickel and molybdenum for superior toughness and tensile strength. The nickel gives the toughness, the ability to take many cyclic impacts and resist cracking while the molybdenum gives the tensile strength characteristics.
The small end of the rod has a high silicon bronze bushing and dual oilers and the beam end of the rod where they affect the rod’s strength less than at the more common location at the very top of the rod small end eye. The bores of the big and small ends of the rod are machined to tolerances of +-0.0001″ and are balanced to within 1 gram of each other.
The K1 rods are forged in a die that forges in the big end hole. This means the metals grain flows around the big end and the rod end cap. This is the best grain orientation for a rod. To improve fatigue strength the K1 rods are shotpeened after machining to give the rod a fine-grained compressed skin where cracks have a hard time propagating.
K1 rods are H beam in profile. We think that H beams are the best profile for rods as they are strongest in the direction of bending in the stresses a connecting rod sees. We are not sure why some companies make I beam rods other than its easier to forge them in near net shape.
A rods fasteners are very critical for its reliability and K1 uses 5/16″ ARP 2000 bolts. ARP 2000 is an alloy that has a tensile strength of over 220,000 psi. This exceeds the strength of typical high-grade bolts and far exceeds the strength of OEM bolts.