Cruise advance is very important. But more is not always better.
At steady-state cruise rpm, the engine wants a ton of advance, until it wants not one degree more. With an unmodded Vcan in a factory D I'm pretty sure it would be almost impossible to give a high-compression engine, too much; even up to a cruise-rpm of 2800/3000.......... unless you are one of those guys who insists on running all-in-timing at 2800 or less.... lol..... even then, I suspect it could use more.
However, chasing the perfect cruise-timing is kindof a diminishing return. Your engine could plateau at some mpg with say 48/52* timing, and not show any better mpg with any more timing.
On the flip-side; if you are cruising at 2200 rpm with 25* advance and no Vcan , well, .............. you are leaving a lot under the table. My Eddie headed 10.9Scr 367 running at 205*F,likes mid to hi 50s there, being just on the plateau, with up to 63* showing very little change.I don't know that an iron-headed 360 would need/want/ or accept, that much; I suspect not.
At 2200rpm, the factory V-can D would be hard pressed to deliver more than 40/42 with 14* initial.
