Street/Strip Torque Converter Test - Stalling For E.T.S

Torque converters have been the subject of heated discussion in performance circles since their introduction. What stall is right for my car? What does diameter have to do with stall? Who makes the best unit? The list goes on.

We decided to answer some of these questions by testing Pro-Formance Transmissions' Dynamic 9 1/2-inch street/strip torque converters with real-world drag testing. The test vehicles included a '74 Challenger with a slightly-warmed 360/904 combo, and a '67 R/T 440/727. Our approach would be to "rollerize" the 727 internals in the R/T, then install a new 9 1/2 inch converter. Both the E-Body small-block and the B-Body big-block had 10-inch converters, but were totally different combinations (car weight, aerodynamics, and power band). We were confident these new 9 1/2-inch converters would prove their worthiness in our pair of street/strip machines.

The Challenger
When we built and strip-tested our Challenger with the 360 and Pro-Formance 904 transmission, we wanted to strip-test the stock 10-inch converter against the Dynamic 9 1/2-inch unit. We felt our 360, with its mild Summit cam (.441-inch lift and 218/228 degrees duration at .050) was a good match for the stock 10-inch converter. A conversation with Frank Lupo of Dynamic Converters/Pro-Formance Transmissions assured us that these new 9 1/2-inch units could be custom-built to match our combos while lowering our elapsed times. We would strip-test the converters at Raceway Park in Englishtown, New Jersey.

While the Challenger was given time to cool down from the 90-minute drive to the track, we mounted the 26x9 Hoosier slicks. Our first baseline pass with the stock 10-inch converter netted us a 12.88 e.t. at 104.05 mph. A minute later we staged again and turned a 12.84 at 104.15 backup pass. One more hot lap for good measure posted us another 12.88 at 104.32. Our 60-foot times were 1.81, 1.82, and 1.83, respectively, for the three back-to-back runs. With a solid baseline under our belts, we pulled the Challenger under E-town's timing tower and set it on jack stands. We lowered the tranny and removed the stock 10-inch converter, replacing it with Dynamic's 9 1/2-inch unit. Even while taking pictures we still thrashed it back together inside of three hours. We filled the Pro-Formance 904 with Redline synthetic racing ATF, and the E-Body was taken on a five-minute ride, checking for possible noises and leaks. We then rechecked the fluids and were ready to fly.

Confident with the newly installed converter, we pulled our E-Body into the staging beams. Wanting to give both converters a fair shake, the launch was set at the same 2,000 rpm. The holeshot and the trip down the track felt much better, and there was not as much drop-off in rpm at the shift points. The stock converter dropped off noticeably at each shift. The 9 1/2-inch converter allowed the Challenger to stay in its power band, and give us lower elapsed times. The first pass confirmed the seat-of-the-pants feeling with a 12.64 e.t. at 104.71 mph with a 1.73 60-foot. A backup run two minutes later produced an even better 1.71 60-foot time and quarter-mile run of 12.62 seconds at 104.73 mph. We were blown away with the results-a full 1/10 in the first 60-foot, a total of 21/410 in the eighth-mile, and another 2 2/100 through the end of the quarter. As an added bonus, this converter picked up trap speed as well. Usually a higher-stalling converter will show a loss in mph-not so this time.

Unfortunately, we ran out of track time. On the ride home, the 9 1/2-inch converter cruised at the same rpm as the 10-inch unit at any given speed-all this in a mild street combo we didn't think needed a higher-stalling converter.

The Veteran
Readers of the now defunct High Performance Mopar will remember when a converter test like this was performed on the R/T. Five years ago we replaced the 11-inch converter with a 10-inch unit and found noticeable gains. This time we'll add a little twist.