Proflow does not sacrifice quality for a low price--you get both with our aluminium cylinder heads. The lightweight heads are cast from A-356 aluminium alloy with a large choice of engine, for SB & BB Chevrolet, LS Chev Holden Ford SB 289-351W, 302, 351 Cleveland 2V & 3V & BB FE, and Chrysler SB & BB. They have phosphorous bronze valve guides, and ductile iron valve seats for use with unleaded gas. They're also end-milled and drilled for accessories. The fully assembled heads have stainless steel valves, high performance valve springs, 7 degree valve locks, rocker arm studs, and guideplates. Perfect for your Mild or High performance Hot Rod.