86 Chevy 350, burnt valve?

I just purchased an 86 chevy with a 350. It has a bad miss in the engine. I took it to a local guy I've used before and he determined it had a burnt valve on the drivers side 3rd cylinder. When you pull off the spark plug wire there is no change in the way the engine runs, so I do know there is a problem, but not sure what it is. How can I be certain it is a valve problem?? And is the only way to fix, pulling the head and having it reworked? Thanks

1st thing to do is check the basics. Make sure you have spark going to the cylinder. A bad plug wire or cracked plug would also make a miss that doesn't change when the wire is off.

2nd would be to do a compression test, If there is no compression or very low compression in that cylinder compared to the others then I'd assume the next step would be to remove and inspect the head.

Just my 2 cents but looks for the simple stuff first!