These MGB aluminum cylinder heads will improve performance with better intake porting and revised combustion chamber design. Made of aluminum alloy, they are less than half the weight and cool better than a cast iron head. Set up for unleaded fuel with hardened seats and silicon bronze guides. A good investment in durability as the cast iron heads are so prone to crack. Complete and assembled with valves and uses stainless steel exhaust valves and dual valve springs. Ready to bolt on.