Thanks once again for the though provoking images and information!
I can’t help but notice there is what appears to be a Ditch or Dam on the backside of the intake valves. My first though is that would not be great for flow/performance, or is this a mechanism to increase fuel atomization, trading flow for better combustion efficiency? It seems that at the rpms generally associated with this engine and given multiple injectors per cylinder, fuel atomization would be pretty good. Is there actually a problem with raw fuel wetting of the ports that this type of turbulence generating mechanism might help? Or, do these engines run in batch fire mode (two squirts per cycle) that dumps raw fuel in the intake track at low air flow times which then congregates around the back of the valve at the seat/throat area?
Next it kind of looks like the valve seats on the head near the back edge of the valve face, the valve face looks to be a single angle and very wide? None of which at least as far as I am aware is a good thing for flow, performance or durability. Why would you want to have all of that valve face sticking up above the valve seat and in the chamber? Seems that extra valve diameter in the chamber would also cause more shrouding issues near the cylinder walls? That darker band around the valve face at the back is exactly what a valve seat looks like after a slight lapping to the head, at least in my book.
Our normal mild street performance valve face has a minimum of three angles on the face of the valve, a valve seat angle with top and bottom cuts differing from the seat angle by no more than 7 degrees. My understanding is that any abrupt change in angle of a surface greater than 7 degrees can generate turbulent non-laminar flow, something we have always assumed was not a good thing in and around the valve seats particularly from about ¼” to ½” (6mm to 13mm) above or below the valve seat. Our racy stuff gets more bottom cuts to blend the seat angle to the stem to head radius of the back of the valve. Following this general prescription has in general most times netted improvements in flow numbers as well as demonstrable performance increases.
Or, is this just a box stock valve blank put in the head for demo and or imaging purposes, and I shouldn’t read anything into the images?