As part of the combustion chamber work I also completely polished the remaining areas and blended away any sharp edges or contours. Anything that is sharp or pointy is a bad thing in a cylinder head and in the case of a combustion chamber can lead to detonation among other things. That’s about it for the grinding and polishing on the heads. I could get some more out of these castings by performing some more aggressive porting and shaping techniques but that is
not part of this plan. That sort of thing gets into the realm of really having to know what you’re doing and having a flow bench to check the results. Even knowing what your doing is still no guarantee things work out like you plan when it comes to cylinder heads, trust me.
As one last thing to try to get my goal of 300cfm without any fancy port work or touching the factory valve seats I decided to try a couple of different valves. More specifically the shape of the valve margins and “back cut” angle on the valves. I noticed that the factory valve job on the intake seat has the edge of the seat right at the outside edge of the valve diameter with the 2.02” valves. That’s a good thing and allows the airflow the largest area with which to operate over the seat. It also gave me an idea and it worked out quite nicely.
On the left is the Ferrea 2.055 and 1.600 valves, to the right are the furnished RHS 2.02 and 1.60 valves.
I grabbed one of my test valves I use for trying different things when I port heads and such and installed a Ferrea 2.055” diameter intake with a factory back cut and a Ferrea 1.600” exhaust that has the margin of the valve radiused from the face of the valve all around to the 45*seat surface. I have found over the years that most heads like to have an exhaust valve with a rolled margin. It makes it easier for the air to get around the valve.
The idea with the larger by .035” intake valve was to give the air a little bigger area to get around and out of the port when it transitions into the chamber. This usually improves the low and mid lift flow numbers without hurting the upper lift numbers too much to negate the gains. In the case of this head it helped where it was supposed to and didn’t hurt a damn thing! I love it when a plan comes together!