Replica Knucklehead-style cylinder heads, cast from aluminium. In addition to the large weight saving of approx. 4 kg per head, this also results in significantly better heat dissipation. The design corresponds to the "Big Port" heads as built from 1940-1947. The standard size press-fit valve seat inserts are not machined but are made of hardened material for unleaded operation. Steel thread inserts with serial thread are mounted for the head screws. These heads have all the important details like cast-in numbers and foundry marks of the series templates. This makes them a formidable replacement for worn-out stock heads, or for building a factory-look performance motor, especially when painted black.