Basic Tuning: HELP!

It's not common, but not unheard of either. I wouldn't automatically suspect a slipper damper ring.

What is your timing now? With the small 318 chambers, and mild cam, I would suggest 5 degrees BTDC with the vac advance unplugged. Does it ping there? You (generally) want as much timing as possible without ping.

Don't even try to fine tune the carb until your timing is set so the engine wont ping. And when you do need to set the carb, the Edelbrock owners manual has a lot of great info. I believe you can download it from their site if you have lost the one which came with your carb.