Yes, i did enlarge the axhaust port, As you can see it`s wider and higher.
Widening an exhaust port can be done to 67% of the bore. In this case it`s 0.67 * 45mm = 30mm. It can be wider, but then you need to have good piston-rings.
The timing can gives you the hight of the port. I wanted my exhasut on 180 degee, with a blowdown of 25. Blowdown is: (exhaust-timing - timing transferports) / 2.
This is a value who gives an idea about the caracter of the cilinder. 20 is lots of torque, 30 is high power.
I raised the cilinde by 2mm, that gives a transfer timing of 130 degree. Then i had to choose a blowdown value, i schose 25. The exhaust port will be open 130+(2x 25) 180 degree.
Then i calculate the hight above the exhaustport, from top of te port to the top of the cilinder. I do this with a program called: Jaaps puch calculator.
Now the program calculated fo me what the hight above the port needs to be, you can enlarge it.
In original state, the hight above the port is for example 25mm. If you know which timing the port needs to be, you calculate the new hight. If the new height is 23mm, then you know you have to raise the port 2mm, to get the wanted timing.