408 ideal rough

I have a 410 with a 232/237 @.050. The LSA or lobe centers are at 104 ground 4 degrees advanced. It idles very loppy at 800 RPM. Ask what the lobe center or LSA is. If it's 108 or less that will make the idle very choppy. Check for a vacuum leak. Spray some brake cleaner around the intake ports. If the idle changes, there is a vacuum leak. I have 16 degrees intial and 37 degrees at 2000. I live ar 4000' so I can get away with that. As stated before 34-36 total is very OK at at sea level. If you know anyone with a 600 or better known carb, put it on the engine and you will know right away if the carb is the problem. Hope this helps!