I bought some burrs from Enco Tools.... they have worked well on my 6 cylinder head porting
1/4 inch diameter shaft for my air grinder , various shapes. single or double cut design worked for me to rough out the shape.
I had some stones on hand to smooth out the cuts.
With porting , remember : " less is more" when you do not have a flow bench or the related knowledge on porting
Some people are like Slinkies... Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs.