440 total timing

If I put more than 32 degrees total timing into the motor, it starts fluttering and missing out. Runs OK at 30 degrees total timing, but you can still hear it fluttering at cruise speeds. There is no vacuum advance hooked up, this just makes it real bad. Initial timing is at 8 degrees. I once read that I should have closer to 36 degrees total timing, though I know this doesn't always hold true. I would like for initial to be more around the 10-12 degree mark, and the total will have to stay at 30 because that's where it runs at. I guess I should modify the slots on the mechanical advance to allow only 20-22 degrees of movement. I am just asking if there's something I am missing here? The plugs are a nice golden brown, so it's not lean.