Diamond has created new domed drag racing pistons for two popular Brodix big-block Chevrolet cylinder heads: the NRC-SR20 and the Head Hunter.
Forged and machined from resilient 2618 aluminum, these new pistons are available uncoated or finished in the Diamond Double Coat. The Double Coat combines a hard-anodized protective barrier etched into the pistons, both inside and out, with a molybdenum skirt coating that insulates it from heat and reduces wear. As these pistons operate in race engines generating 1100 to 1250hp plus nitrous power, the double-coat is a wise precaution.
On the piston crowns the depth of the inlet valve pockets to suit the NRC heads measure 0.360in; the Head Hunter 0.340in. Both pistons accommodate 2.400 inch inlet valves. Because the 1.900in exhaust valves, used in both heads, operate within the combustion chamber no valve pocket provision is necessary.
Included in each kit is a standard ring pack the dimensions of which are 0.043in, 0.043in, and 3mm oil control ring. The placement of the top ring down from the piston crown is 0.260in (NRC-SR20) and 0.300in (Head Hunter). Side gas ports are provided on both pistons. These transfer combustion gases to the inner regions of the top ring grooves, maintain ring contact with the cylinder wall, and promote dependable ring sealing.
In the pin bores two holes lubricate the H13 tool steel piston pins, which are provided with each kit. These holes are connected by an oiling groove which is fed via passages from the oil control ring grooves. The pins are retained in the pin towers by double spiral locks and to combat high operating pressures, the pins boast 0.185in thick walls.
Below each pin boss a rib side-relief is featured. These are integrated into the lower regions of the pin towers and provide crucial support to the piston skirts. Finally, inspired by the popularity of the Brodix heads, these new pistons are covered under Diamond’s “one piston no problem” program.