To the best of my limited understanding of the system, VVT is fairly simple mechanically, but it has a pretty sophisticated computer control system. The cam(s) start out advanced for low speed torque, and oil pressure and a helical 2-piece timing gear is used to retard the cam position for high speed horsepower and to control combustion chamber temperature to reduce the formation of oxides of nitrogen. That's why VVT engines usually don't have an EGR valve. The mechanical assembly of the VVT system should be pretty straightforward- - - -just follow the service manual procedures for engine assembly.
Cadillac tried cutting out cylinders with their V8-6-4 system back in the early 1980's by using a movable rocker arm pivot to disable intake valves. The system was pretty good at dropping cylinders out- - - - -and terrible at getting them back into operation. Those engines got replaced with conventional V8's under warranty almost immediately!
Jerry
