Cylinder has spark but not firing..

No I'm not using the tin intake gaskets I have composite in it. Those plugs are out of the motor from when I first got the car. I did have new ones in thinking they were bad so I found 2 plugs just to put in to see If it made a difference. This carb is an old Holley that came off a 427 motor. I looked up the number on the choke horn and it's a 4815 list. Actually, I re looked it up its a 780. It is rebuilt. I rebuilt it with a friend a while ago. I had it on my 318 on the previous car and it worked fine. I could tune both sides and throttle response was great. Now the only issue I'm having is I can't tune 1 side of it. You screw the needle down all the way and it doesn't do anything.