I recently completed a heads+cam project on my car to increase horsepower. I ended up falling about 50hp short of my goal, and am looking for every little knob I can turn to eek out that last little bit. I've learned some things recently that have led to some conclusions, which I would like validated (or corrected!)
I had previously believed running more timing advance (delivering spark ahead of TDC) was desirable - just before the point of knock. However, that does subject a portion of the mixture to burn during the last part of the compression stroke - effectively not contributing to the power stroke, and providing a little extra resistance during the top of the compression stroke. The reason this is still done in practice, is because the flame speed is finite, and you need to start the burn early enough so there's max pressure just a bit after TDC.
So conclusion #1 - I can actually make more power by running less timing, IF I can get a faster flame speed. Basically I would like to minimize the amount of the charge that's burning during the compression stroke, as long as I still get peak pressures just after TDC.
Ok, how can I get a faster flame?
1) Larger spark gap, so long as the coil is sufficient.
2) run closer to stoich, which is hard to do at WOT, since typically extra fuel is added to lower temps. But if I add a significantly cooler thermostat (say 30 deg), then maybe I can go a little leaner, from say 12.5 to something much closer to stoich.
Does this sound right? Does it work in practice?