Roger, what i mean to say is that if you leave the short turn steep/vertical, the flow will not be good. 1.88 valve will make the turn steeper without porting them and without a good throat cut will also leave a big ledge just under the seat.
If one were to cut for a 1.88 valve and do no porting, it will flow less than a stock 1.78 as is from the foundry.