I believe the head design of all multi valve engines are very poor, they only work because of the multi valve configuration, the ports are all too low for a decent angle to the back of the valve head.
SNIP
Just curious if you have looked a 4200 head close up..
The valves are canted over toward the ports about 35-40*.
If the port and valve size was so poor then explain why each intake valve contributes ~175 cfm at 0.500" lift at 28" water pressure on a 1mm OS 2006 head..
