Ok you need to seriously stop messing around and MAKE your timing do what you want it to do. 42 is too much and likely the reason it’s rattling. Forget vacuum advance FOR NOW, after you get a good baseline you can add that in later. Almost any mildly modified street type engine will run pretty good with 18 or so initial and 32 total with one light and one medium spring. So I always recommend that as a starting point. So find a way to limit the mechanical to 14 degrees, set the initial at 18, verify that as you rev the engine it increases to 32 around 3000 rpm or so and then, only then you can start tuning on it.
