The '64 (Gen II) 426 Hemi revival incorporated a 58-degree included valve angle, but the machined combustion chambers were slightly rotated toward the intake side of the head. This was done to reduce overall engine width for easier assembly-line body-drop activity. The 172cc combustion chamber volume required a large (and heavy) piston dome to yield high compression for race duty. Naysayers don't like to admit this isn't a "true" Hemi design. The vast majority of OE Hemi cylinder heads were cast iron except those aluminum heads installed on the approximately 201 A990 Super Stocks built in 1965. Currently, Gen II Hemi heads are widely available in both materials.