360 Tune Up

Joe,
Was expecting the answer that idle was better with 25* init. My engine engine idles with 48* [ yes, 48* ! ]. So much BS with this topic.
The 'one size fits' all dist doesn't exist. If you want the best, you have to dial in your own curve & be prepared for some trial & error work.
The engine speed & vacuum increased with 25* because the engine is making more HP. It likes the extra timing at idle; it may like even more.
Get the highest idle rpm you can by toggling the dist with the engine idling. More cam needs more timing. Once you have that, you have to decide how to get it permanently. If it likes 35* initial, the starter probably doesn't.....
The fix here is to lower the initial to where the starter is happy [ 25*? ] & add the rest using vac adv hooked to manifold vacuum. In the example, you would need to limit the travel of the VA plunger so that it only adds 10*. You should also use an adj VA unit with the Allen Key fully CW to start with.
The curve in the dist will have to be modified [ shortened in this case ] to provide the total timing under load [ VA goes to zero under WOT load ].
Engine will run cooler/smoother at idle & have better tip in response.