This next picture shows one of the chambers with an Intake and an Exhaust valve. The valves themselves have purple lines on the seat faces to help identify the face and back cuts. The face is ground at roughly 44-44.5 degrees and the 30 back cut is 30 degrees to aid the air flow transition from the back side of the valve to the seat at low valve lifts, less than .100? lift.
On the valve seats in the head, I marked the angles in green, with the offset green mark being the actual 45 degree valve seat face itself. The intake on this head has 5 angles, the exhaust has 4 angles. I try and get 5 angles as often as I can, but several factors dictate if I am even able to or not, such as new seats, valve head size, etc. With every head that we do, we are able to open the throat of the valve seat itself at least .040? sometimes as much as .060? over OE. This is like going to a larger valve without actually installing the larger valve itself. This modification is really only good for really high valve lift flow, at low valve lift, it doesn?t help. Of course actually installing a larger valve allows me to open the throat of the seat even further, but for most mild to moderate street L-series, this is not needed. For the Intake seat, the top angle in the chamber is 15 degree, then 30, then the 45 degree seat itself, then 60, then 70, then the bowl hog cutter which is the Blue marks, (the bowl hog is either 75 or 80 degrees, I forget which, forgive my poor memory), and then the port walls themselves. For the Exhaust seat, the top angle is 30 degree, then the 45 seat itself, the 60 degree, then the 70 degree and then the bowl hog. The green circle just left of the intake seat is the chamber wall relief cut which radiuses the 15 degree cut into the chamber wall and roof, (the 15 degree and chamber radius is actually on one cutter, as well as the 30, 45, and 60 degree cutter).
