Not all torque converters...
Not all torque converters are the same. Consider using a converter designed expressly for stock car racing. These converters will feature a stall speed much lower than those built for drag racing, and the best will also be approximately 98 percent efficient-meaning more power to the rear wheels.
"As far as TCI, when we build a torque converter for stock car racing, we put in special stator and fin combinations that allow us to give the racer maximum converter lockup. As much lockup as you can get with a fluid coupling mechanism and yet have good torque multiplication. It has come from extensive testing specific to stock car racing-which is certainly different from drag racing-and it makes a difference. The biggest thing is that our converters are more efficient, even at the low stall speeds. For example, if you run a stock torque converter, or a stock replacement converter you can get from your local parts store, slippage can be anywhere from 12 to 15 percent. That's on a perfectly good converter built to stock specs that has no defects in it. Our converters are 98 percent efficient. That means we can cut your slippage from 15 percent down to 2 percent. And you'd better believe that makes a difference on the racetrack."
Ultra-High Performance Options
So far we've only talked about performance options that require only a minimal investment. But there are even better options out there for racers looking for the ultimate in performance from their automatic transmission. For teams racing the Turbo 350, TCI has developed what it calls a Posi-Drive technology that provides 100 percent fluid coupling. It requires a special transmission and converter package from TCI, but the result is no power loss, instant acceleration as soon as you hit the gas pedal and improved engine braking. Efficiency is so good that TCI's engineers say you can expect to see your engine run 200 to 400 rpm less with the Posi-Drive setup.
If your rulebook doesn't limit what transmission you can run, you may want to take a look at a Powerglide setup. Miller says the Powerglide has an advantage over even the Turbo 350 in that it has a lower rotating weight at approximately 20 pounds and pulls less horsepower. That means more of your engine's power is available at the rear wheels. Miller says tests have shown that a well-prepared Powerglide pulls only 18 hp in high gear. Additionally, TCI offers Powerglide transmissions with a complete mechanical lockup, meaning no power losses from a traditional fluid coupling system.
If they aren't disallowed in your rulebook, you may want to think about running a Powerglide automatic. Compared to most other automatic transmissions out there, the Powerglide has less rotating weight and pulls less power from the engine in high gear.