It's always been my understanding that as RPM increases the vacuum decreases and therefore MAP increases. So looking at the Main Spark Table, you see that as RPM increases and MAP increases, you move across the table from left to right and top to bottom (in a diagonal pattern). So I would expect to see the degrees spark increase as well. However, every stock BIN file I look at has the exact opposite. The degrees spark actually decrease, essentially retarding the spark. What's going on with this?

 

That would be correct, except one of the legs of your foundation is flawed. MAP doesn't necessarily increase as RPM increases. In fact, at any given throttle opening, just the opposite is true. The absolute highest vacuum an engine will achieve is at high RPM with a closed throttle (decelleration). A fixed RPM and a more open throttle will cause a lower vacuum (higher MAP), but as RPM increases vacuum will as well.

But there is another thing to consider. Higher RPM and a lot of intake air (open throttle to the point of lowered vacuum) usually sharply increases dynamic compression in the cylinders. Advancing the spark too much at high cylinder pressures can lead to detonation, the kind that drives the piston back down and breaks rods, wrist pin bosses, etc.

You can usually safely get a little more advance than the stock tables allow, but need to make sure the KS is working, retard steps are large engough, the attack rates are correct, and your cylinder pressure and fuel combustion rate are no so high as to create or allow detonation. Higher octane fuel burns more slowly, which is how you can get away with a little more advance. Even "regular" fuel can allow more advance if you are willing to push the edge a little.