I thought you said that the guide was "wasted?"
So then you tapped a 1/4" valve bore with a 5/16" tap to try to knurl it?
Now you are trying to drill to fit a .310" guide in a .305" or .307" hole?
And you'll finish ream the guide with what size drill bit?
All without centering the guide in the seat?
When you get done with your experiment, install the new valve and shine a light in the port and let us know if you see light around the face of the valve and seat.
You're right, this is not an F1 engine or million mile diesel engine.
I'm all for the DIY'er, but you sir, are in way over your head and capabilities.