[longhornchris04]

Higher octane gasoline doesn't burn significnatly faster than the lower octane stuff... just more predicatably and w/ less chance of unintentional detonation. As a result, even with race gas you still have to get the flame front across the cylinder to the far side. With high domed pistons this requires a lot of advance - hence the negative work, or for high enough RPMs just can't be done - resulting in unburned fuel and lost power.

Ignition timing is complicated... almost a black art, but the science is fairly straight forward. The goal is to fire the plug early enough that peak pressure occurs just after TDC. This isn't, the only consideration though. Others include
- complete combustion - unburnt fuel/air is wasted power
- knock protection - from the spark side not allowing pressure/temps to exceed fuel autoignition conditions (higher octane, higher autoignition characteristics)
- Emissions - the higher the combustion temp, the more NOx produced.

To complicate matters, a lean fuel mix burns faster, a rich one slower. A rich mixture is also initially cooler, as the fuel absorbs heat during vaporization. This is why going lean is so dangerous - your chances of detonation go way up as the mix is at a higher initial temperature and generally more volatile. Its also why vacuum retard was added - it is partially tied to leaning out the idle/part throttle while the fuel system leans out the mixture for emissions & fuel economy reasons.

Additionally, the higher the RPM, the increased chamber turbulence better mixes the fuel/air. This is why spark advance is "all-in" early... the increased mixing increases combustion speed enough that more advance isn't needed.

Of course in a more modern spark tables take into account both RPM and either MAP or MAF inputs to correct the timing for RPM and load. These are tied to the fuel tables to run closer to the limits.

So, twin-plugging effectivly cuts the chamber in half which reduces the amount of advance needed. This in turn causes
- more complete combustion, especially at high RPMs - more power
- increased dP/dt - less pressure rise before TDC - less power lost
- more stable combustion - less mix for each plug to ignite

I'm sure its possible for you to run a "small" bore high compression in single plug configuration if you keep the timing conservative, but at that point you've created an unbalanced engine, with your ignition being the limiting factor.

In my opinion, this is no better than building a 400hp motor and trying to mate it to an unmodified 915 gearbox... you won't be able to use it to its potential.