I have been given a verbal evaluation on the intake side which I hope I am relaying accurately:
The entire port is basically a short side turn with the first one encountered being the sides which flare out 90 degrees. As lift increases the charge fails to navigate this turn and bounces off the back wall. With a divider in place (several forms tried) the charge is diverted but only toward another wall and only at high lift. Without a raised floor and roof or other downward bias there’s too much disorganization rendering bowl, roof, and guide improvements negligible so that first turn really pollutes direction and is basically the deal killer.
With the openings on the manifold being of sufficient size to support the valve being used plunging in with a reamer/etc. likely causes more harm than good by aggravating the ports worst feature at the sides where it opens. The possibility of boring to insert a sleeve with back to back D shaped ports was examined but there is not enough space to make that a workable solution as the direction change required can’t be met. A reasonable attempt (by hand) at radius improvement on the sides where it flares out may show some positive benefit and will be investigated. A lump on the floor at the opening was tried as well as side bulges to alter the turn some all with no noticeable benefit.
As many sources will say the most important areas regarding flow are those in the last half inch of distance in each direction from the valve seat and this case appears no different. I’m told the approach angles are less than ideal and can’t be improved as the material is simply not there however trying a bigger valve may allow for improving the approach/depart geometry and unshrouding so that is where the focus will be from here. I’m told there can be a very fine line between a throat that is just right and one that is too big so small incremental changes near the seat is where most gain is expected. Another item of note was that flow just gave up at lifts above about .350” so further investigation on camshaft design is warranted. I don’t have graphs yet but unfortunately so far there’s nothing much good to see.
