the epoxy in front of the guide will create an "anti" swirl to the natural pattern of swirl natural to the valve placement/position... ls motors have that cast in,,, you can get turbulant airflow, or air disconnecting from the short turn and the vane,, or a particular type of valve job will help the air stay connected as valve lift goes up. everyone has seen air get turbulent or a head loose airflow as lift increases,, what he did with the epoxy will help that not to happen,, and for the head to continue to gain as lift increased

putting more short side on the head with epoxy is not a bad idea..