Ready to shoot my 273

Set idle mixture with a vacuum gauge hooked up to carb. At idle speed (around 800 rpms) set idle mixture one screw at a time by turning screw in or out till you get the highest amount of vacuum, sometimes you will need to reset idle if it gets too high or low. If you have a stock or mild cam you should be able to dial in at least 12in or you have a vacuum leak somewhere (intake or carb gasket). Also try running it with vacuum advance unhooked and see if that changes. Are you setting total timing with vacuum advance unhooked and pluged at carb?