Dead Cylinder?

Hi Guys, I know there's a lot of good mechanics here at FABO and I need a little help. My 318 is fairly fresh from the rebuild a '78 model w/stock 340 cam in it dual exhaust small Holley carb stock ignition etc. I have now a dead cylinder, it's getting fire and fuel and the valve train seems to be working like it should, I havent tried a compression check yet. What could my problem be? Burnt valve?
Thanks!