Econo Performance Torque Converters BM400010Econo Performance Torque ConvertersSuit GM Powerglide & Trimatic, 3500 4000 rpm BM400010 400010 These Converters are budget priced and are intended for mild street engines up to 350 horsepower. They should not be used with nitrous, superchargers or transbrake but are perfect for street cars and hotrods. Stall speeds are based on an engine producing 230lb ft of torque at 2500 RPM. Engines with more torque will stall higher and less torque will stall