Cam shaft and method of manufacture

A hollow cam shaft of the type wherein lubricating oil is distributed to the cam portions through the hollow shaft, the shaft comprising:

• a pipe member having a longitudinal axis and a through-hole along said axis, said pipe having an inner cylindrical surface to be contacted by the lubricating oil;
• means for reducing the volume of said through-hole accessible to the lubricating oil, said reducing means including
• (i) a rod member positioned in the pipe member through-hole at a fixed axial location with respect to said pipe member, said rod member being of a lightweight material compatible with lubricating oil and having an outer surface with a diameter less than the diameter of said through-hole, the volume of lubricating oil in said pipe member being reduced by the volume enclosed by the outer surface of said rod member, and
• (ii) means for spacing said rod member from said pipe member inner surface along said longitudinal axis;
• and
• conduit means extending through said pipe member inner surface for connecting the cam portions and said pipe member through-hole, wherein said spacing means includes a pair of end members attached to said pipe member at respective pipe member axial ends, each of said pair having a recess formed therein, said recess being sized for receiving the respective axial end of said rod member, and located to space said rod member from said inner cylindrical surface;
• and
• wherein said spacing means includes at least one guide strip surrounding said rod member and spaced along the rod member axis.