The torque converter is like the turbine you see in a jet engine. Inside the T/C there's a front and a back, the propeller, and the impellor. How the converter works is that when transmission fluid is pumped into the converter, it flows down the rungs of the propeller, which is connected to the engine/crank end. When the motor turns, it flings the transmission fluid onto the impellor, which is connected to the transmission side. This action of flinging transmission fluid is how power is transferred to the ground from the engine. This is why auto transmissions have a very bad reputation for NOT being fuel efficient, because even at higher RPM's, there's still slip and loss of power. Because of that, almost all newer T/C's (like ours) have a lockup feature, which presses a plate between the propeller and impellor, "locking" them, and removing the majority of the power loss.

Now since the TC has to have slip or the car would stall, the propeller and impellor are ground and aimed in such a way, that they will slip and sling oil around until a certain rpm is reached. On a stock converter it's 2400RPM. This means that when you hit the gas from a dead stop, the motor spins up to 2400RPM, and the transmission starts turning until both are turning at approximately the same speed. Then because of all the oil flinging around, the slip isn't much of an issue anymore, and the motor continues to accelerate. What a high stall does, is increase the slip, so that when you step on the gas, the motor revs up (to say 3500rpms) and the larger amounts of power at that rpm are then transferred to the ground, allowing the car to accelerate faster from a start. The tradeoff with a converter like the Howell Unit, is that for the extra slip you create to have the higher stall, you lower the converters efficiency. So although you'll be stalling higher you'll need more power to overcome the loss in power from the extra slip. Be forewarned, this extra slip generates extra heat, extra heat is bad, as it will prematurely weaken parts and cause them to fail. For this reason you should install a tranny cooler, to preserve your transmission. You will loose a little street drivability, espically with a "loosened" converter, but not so much with a "true" converter. a true converter will behave much more like stock, but with simply a higher "off the line" RPM limit.