Please don't break your car on purpose. ?
why , ?

Originally Posted by jdraughn

Wow, that thing is rock solid. Do you have a link detailing what components you used, and how you built your drive train?

It's just slot-car gears and a RadioShack-esque DC motor. It doesn't draw much current, really, so the bridge is not taxed at all.

From the experiments I have conducted with random assortment of mosfets, the p-channel ones always get waaay hot, so I was going to try to go with a boot strapping high side driver like the MCP14700, but from your experience and results, maybe I need to buy GOOD mosfets. Which mosfets did you end up using, and what motor are you driving with them?

Are you sure your P-channels are fully on, and not stuck in the linear region? They have higher on-resistance than N-channel, but not by that much.
Really, as I found out, "GOOD" mosfets means looking at more than just the current rating. There is a trade-off between current rating, gate-capacitance, and to some extent cost. And even the "current" rating isn't very straight forward, since it depends on how quickly you can switch them on/off, switching frequency, shoot-through-avoidance, etc.

Having done it once (to learn), if I were to need another h-bridge, I would probably get an off-the-shelf unit like those seen here:
http://www.pololu.com/catalog/category/82