The stock angle cut on those are 45 degree one cut angle with a nasty lip. I cut them 44 degree, then top it with a 30 degree, removing the lip alltogether. This gives the air flow going into/out of the chambers less resistance passing by the valve therefore allowing more air at a higher velocity

Another part is the 44 degree cut, when matched to the 45 degree seat will have a "wedge" effect on the valve keeping a good strong valve to seat seal.