X-Head Porting....
1/4 inch width or length? I bet a smaller round burr would be decent in the areas around the guide boss.
Both. The length adds to the cutting edge. You don’t want to cut with both sides of the burr. Think about how the burr is ground. If you put the burr against two surfaces, it’s on a climb cut on one side of the burr.
So as you work the burr, it’s trying to go down in between the guide and the side of the port, and it’s trying to climb out from between the guide and the side of the port.
So you need to determine how much clearance you have for the burr and start with a smaller burr and work your way up to bigger burrs.
I personally do not like tree shapes or cylinders and I don’t like long burrs. The more cutting area you have, the harder it is to control.
I can tell by the corner radius you leave your burrs are too big for how I finish a port. A radius like that works if the port has enough cross section to feed the valve you are using. When the valve is already too big for the port, a big corner radius will kill power.
Look at the W2 intake port. It has an oval shape, but the cross section is much larger than any production port. And, the W2 port is way too small for 340 inches at 8000 RPM or more, or if you burn alcohol. You have to consider fuel used when porting. Increase the displacement and the cross section has to increase.
Just some things to consider as you learn to port. There is much more to it than making the holes bigger. Shape is everything, flow is secondary at best.
I’ll take some pictures of the few burrs I use tomorrow. I went through many burrs before I settled on what burr made the shape I wanted as my eyes see the surfaces.
I have friends that port, and port well. We compare burrs every now and then. We have almost no burrs in common, but they can get the same shapes I do. Their eyes see the shapes differently than mine, so they use a different burr to get that shape.
I say that only to let you know what burrs I use (or anyone else uses) may not work for you. You just have to try different burrs to get the shapes you want as your eyes see them.