These cylinder heads are the Edelbrock Performer RPM FE (PN 60087). They will work in place of low and medium riser heads and are NHRA legal. They were bought as bare castings and were assembled with 2.09-inch-diameter intake valves and 1.66-inch exhaust valves. The valves are equipped with titanium retainers and 10-degree locks. They have 170cc intake ports and 76cc combustion chambers. The bare heads cost $1,297 per pair while the CNC-porting, valves, and assembly hardware were priced at $1,157.