The edelbrock heads have a 58 cc chamber and you can buy them like I did with the good springs for the hydraulic roller cam. My iron rams had the hughes 1110 springs and with the same cam would shut down at 6000 rpm. With the edelbrock springs I can twist that hydraulic roller to 6500 witch may be part of the performance gain but I still would have a hard time believing that the 2.02 valve would make the iron ram perform with the edelbrocks.:???: