In addition to the small-block, RHS also offers heads for Chevy big-blocks ... Compared to the GM 906 castings, the Pro Torker Vortec heads offer an additional 27 cfm at .500 lift.

For this episode ofEngine Masters, presented by AMSOIL, we grabbed a set of as-cast Chevy Vortec heads, 906 castings in this example. The stock 170cc ports were left untouched, along with the 64cc ...

it created one of the best off-the-shelf iron cylinder heads ever made for the small-block Chevy. The 906 and 062 Vortec heads (referred to by the last 3 digits of their casting numbers ...