360 timing advance problems

67Dart273 said

Actually you "can" (notice " "!!) connect to manifold vacuum, but the factory was to ported. Some people INSIST that manifold vacuum is "better" but to do so you must have the mechanical advance set up accordingly, and obviously set initial timing accordingly.

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^^^This^^^
The key piece of information missing so far is the knowing what distributor you have.
And even with knowing the distributor, the advance curve often isn't what you think it is, or what the manufacturer says it is. Best to measure timing vs. rpm from the slowest rpm you can get it to run at, then every 200 or 250 rpm as high as you and your tach are willing to go.