Understanding Torque Converters
Torque converters are not easy to understand. Luckily, you may only have to understand a few basics to choose the right stall converter. One way is to look at your cam card if you just built or installed a new cam. The cam card will state the RPM range for the cam. The cam will build good power in this range. Choose a torque converter rated about 400-600 more in stall speed over the lower cam RPM range. Consult a qualified speed shop with more questions on choosing a torque converter. Because a torque converter multiplies the torque of the engine at launch, you need to maximize this torque multiplication by choosing a converter in the powerband of the engine. Otherwise, you waste the max torque of the engine if the stall speed is wrong.
How a Torque Converter Works
Torque converters pump fluid through the transmission. Varying the outside diameter and the shape and configuration of internal parts like fins on the turbine or stator will change the stall speed of a converter.