Ok so what if the intake valve was still a bit bigger but not as significantly and the space utilized for a bit larger exhaust valve? I.E. - custom camshaft to be cut - what if instead of 40/35 you size them more like 38/37 and rather increase the ex. duration just a little more? I mean as D said, if you already have an adequate intake valve, why not bring the exhaust valve up to par and just manipulate the cam timing?