http://www.ws6transam.org/Backcut.jpg

http://www.austincc.edu/wkibbe/headdesign_files/image006.jpg

The latter is an extreme example of a back cut, it's not supposed to be that radical. But demonstrates the area that is cut. (Left valve is back cut, right side valve is not)

Edit: one more:



Shows the back cut (removed material in red) in relation to the port and seat area. You can see how the "ramp" would otherwise create a bottleneck between the valve and the seat. In many/most valve/seat designs I would guess?

Last edited by 70Nova; 12/12/13 01:11 AM.