TOUGH TORQUE CONVERTER
A DURABLE TORQUE CONVERTER OF THE RIGHT SIZE AND STALL SPEED WILL MAKE THE DIFFERENCE IN ALL-AROUND PERFORMANCE ON THE STREET AND/OR AT THE STRIP.
A durable torque converter of the right size and stall speed will make the difference in all-around performance on the street and/or at the strip.
With an 825hp Ray Barton Street Hemi going between the fenders of our ’65 Coronet project (alias “Cool Blue”), we knew we’d need a tough, wellbuilt torque converter. Stall speed and durability are of the utmost importance when selecting the right converter for your combination. Having the right stall speed converter has the greatest impact on the performance of your car, whether it’s at the strip or driveability on the street. Depending on the build purpose of your ride, the converter needs to match both your desires and the entire combination. When a converter is the right size (8, 9, 10, 11 inches) and stall speed for your combination, your timeslip and/or street performance will be at its best.
For many, including longtime enthusiasts, it’s somewhat of a mystery in how torque converter functions. We’ve also heard that as it spins, it multiplies the torque produced from the engine to the transmission’s input shaft to help move the vehicle with more force than a manual transmission. This mystery is accomplished by the fluid dynamics produced inside the converter. As this hydraulic power transfer continues, its fluid couples through the converter’s internal components (turbine, stator, impeller pump), thus multiplying torque to move the car down the road and/or track.
The internal parts can be manipulated to get a converter to behave a certain way or have a specific stall speed. The performance and stall speed will be determined by which parts are used to build the converter. The impeller pump fin angles and stator blade design are the primary components used to change stall speed and torque multiplication. A torque converter manufacturer will make changes to each of these parts to dial-in where the converter will begin to stall.
Just selecting a converter off a website or catalog isn’t the best way to get your
car to perform at its best or get the best e.t.’s at the track. All the major torque converter companies will be glad to work with you to help you get a converter that’ll fit your performance goals. To determine the stall speed and what size converter you’ll need, the converter manufacturer will need information about the vehicle’s combination. Specs like camshaft profile, engine power, and peak torque, peak horsepower, gear ratio, tire size, and vehicle weight are just a few of the specs needed. The more info you can provide, the better the torque converter can be matched to your combo for maximum performance.
For our street driver, Street Hemi Coronet, we considered some of the great converter manufacturers like Turbo Action, ATI, Dynamic, Transmission Specialties, and TCI. We’ve used each one of these reputable companies’ torque converters through the years without a single issue. A few years ago we tried a TCI 10-inch Ultimate Street Fighter torque converter. That TCI unit helped a friend’s car run a 10.46 at 130 mph with a previous best of 10.52 at 128 mph using a different brand 10-inch converter. The 60-foot time also improved from 1.50 to 1.46. While street driving it showed less low rpm cruise slippage and better throttle response, meaning it was a more efficient converter with less of that slippage feel. Now five years later, my buddy’s A-body has made over 50 10-second passes, and it has over 5,000 street miles — that durable unit was our deciding factor to go with a TCI Ultimate Street Fighter converter.
We let the TCI technician know the Coronet’s primary purpose was to be a responsive street driver that’ll put down good power when we chassis dyno test and tune. Once the B-body is well sorted out with a few hundred street miles, we’ll flog it once for a strip-test, just to see what it’ll do. Lowest e.t. isn’t our big concern, but with 825 hp at the crank, low 10s should be doable on 275/60R15 drag radials.
Check out the pictures the good guys at TCI took while they custom-built our tough torque converter. TCI says The Ultimate Street Fighter bridges the gap between their full competition units and Super Street Fighter converter. It’s built to handle up to 1,000 hp for extreme street machines, featuring furnace-brazed fins, steel stator, needle bearings, anti-ballooning plate, hardened pre-ground pump hub, and computer balanced. We’ll have plenty of confidence knowing there’s a durable TCI converter teamed up with the bulletproof A&A Torqueflite we built in the previous story. It’ll be plenty tough to handle the incoming, high-horsepower Street Hemi. Follow along and see how TCI builds one tough torque converter.
We chose a TCI 10-inch Ultimate Street Fighter torque converter based on (among other things) its proven reliability in a friend’s 10-second street car. It features a billet steel front cover, furnace brazed blades, steel stator, needle bearings, hardened preground steel front hub, and anti-ballooning plate. It’s all computer balanced to support 1,000 hp.
It’s tough enough to handle the incoming 825hp Street Hemi that’ll propel our ’65 Coronet.
A Torrington roller thrust bearing is placed in the center of the cover before the turbine assembly is put in position. The turbine assembly is connected to the input shaft of the transmission. Fluid flow from the stator and impellor pump force the turbine to rotate, making the car move. Notice the furnace brazing of the fins for strength and longevity.
In this shot, notice how the ring gear was precisely computer welded to the cover at four equally spaced locations for equal balance.
The folks at TCI took a few photos while they custom-built our torque converter to match our vehicles combination for the right stall speed. Here’s a look at the thicker and much stronger than stock Cnc-machined steel cover (engine side) before its ring gear is computer welded in place, and the converter assembly begins.