rlearp,

The 5MGE was designed as a truck engine. It makes good torgue. As it was designed as a truck engine the designers did not see the need for high rpm. The valve train is good and has room for improvement. The cam does not act directly on the valves. It pushes on a rocker arm. One end of the arm is on the valve stem. The other is on the lash adjuster. The limiting factor is the hydrolic lash adjusters (not lifters). There is a pressure regulator to control oil flow to the lash adjusters. At high rpm the lash adjusters tend to go soft. When that happens is the valve springs are stiffer than the resistence offered by the lash adjusters so they colapse preventing the valves being opened fully. Or so my engine builder explained it to me.