Huh?.... Vortec heads are less prone to pre-detonation, so you can run more timing
No. High turbulence chamber design enables faster flame front spread, and requires less timing lead. Quench helps, but dished pistons do not provide adequate quench clearance (0.040 or so). This is also why the "high swirl" intake ports on some 4.3 V6's require less total advance.
You only run enough timing advance so peak cylinder pressure is essentially at, or slightly after, TDC. Too much advance, and the pressure peak will try to push the piston down on the upstroke. This leads to power loss, possible detonation and damage.
On a race engine, or even a boat, which runs at pretty heavy throttle settings, it's better to be conservative on total timing.
Vacuum advance is used on street engines because at part throttle, the "effective" compression ratio is way less than the mechanical ratio, and additional advance is required to optimize the slower flame front spread and achieve peak cylinder pressure at the correct time.
Look at older restrictor plate NASCAR engines. If they accelerated too hard at low rpms, the 14:1 compression wil detonate the engine. However, at high rpms, the limited breathing reduces the effective compression ratio to a manageable level.
They run a methanol rich fuel now, and ethanol has a much higher effective "octane" and will support higher compression. There just isn't as much energy in the fuel itself.
