Close the valves after installing a head. The cam-and-lifter assembly controls the valves and should not be completely installed until after the head is on the block.
There are two major cam configurations on engines: cam-in-block and overhead cam. In the case of the cam-in-block engine, place the rods through holes in the head after installation. These rods push rocker arms, which control the valves. The overhead cam has a more direct relationship with the valves and engages the rocker arms directly. When attaching both types of head, it is necessary to assemble the rocker arms after installing the head.