K1 connecting rods are made from Billet 4340 Steel. Proprietary bolts produced by ARP to K1 specification have asymmetrical threads to equally load each thread when under pressure. Connecting rods are shot peened for improved fatigue life and are finished in the USA using state of the art Sunnen hones. Housing bore tolerances of +/- .000050” (50 millionths) match some of the tightest accepted tolerances in the industry.
The rods have double bridged caps to reduce housing bore distortion and there is no ridge between the blades acting as a stress riser. Rods are weight-matched to +/- 1 gram and boxed with the individual rotating, reciprocating, and total weights conveniently noted for balancing. A special wrist pin bushing material is also used with these assemblies offering optimal friction reduction.