In the 1980s General Motors shifted away from small holes in the cylinder head and pushrod guide plates instead to what they refer to as “guided” rocker arms. These stamped rocker arms use two small ...

Thunder Power's 4-valve cylinder head conversion for big-block Chevys bolts right onto production iron or aftermarket aluminum cylinder blocks. The heads even have the necessary bosses to add an extra ...

Chevy fourth generation aluminum big-block head is readily i.d. 'ed by "bow tie" emblem and new square exhaust ports that exit ¾ inch higher than previous D-port design. You'll have to drill new ...