To be clear, only use carbide if you are porting. It cuts through aluminum very quickly, so you're only using the burrs to get the approximate shape which you then sneak up on with the stones and clean up to a nice finish with the sandpaper cartridge rolls. A perfectly smooth finish is not required, or necessarily desirable on the intake ports. The smoother the better on the exhaust. It's important that the ports be as close to identical as possible in size and shape. If you're new to porting heads in general and SOHC4 heads specifically don't go crazy, follow Hondaman's advice for mild improvements and cleanup. Going too far from as cast it's easy to mess things up without a flowbench.
