What I woul like to say is Promaxx 440 head and Todd Sidewinder head are very nice casting and accurate machining. The material is A356.2, elements such as Fe, Ti, Mg, and Si was under control. Which help the aluminum have better microstructure and lead to better physical performance such as hardness, elongation. The advantage of the casting is the intake and exhauste port are very smooth. Much smoother than RPM heads. Because the casting is using special fine sands in intake and exhaust port. The machining is using modern technology with 4 axises CNC machines. The combustion volume, the position tolerance was under strict control. The machine tolerance is 3/1000 mm. There is someone do it better, it's AFR. AFR tolerance is 1/1000 mm in key positions. In a words, the heads were made by OE standards with is same as GM present cylinder heads production standard. Both Promaxx and Todd is doing great job to make the better 440 cylinder head better. More people try it, more people will be happy.