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Hey, I've been looking in some car part magazines (which will one day be the source of my finacial doom), and I came across some additional stall speed torque converters. Being fairly new to automotive expertise, I wasn't quite sure what they are. What exactly do they do, and what are they made for? Should one have a reccomended setup before thinking of placeing one in? Are they a "one-type-part", or do they come in different ratings? Which ones have you found to be beneficial?

Thanks.
 

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Contributing Sr Motorhead
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School time!

The torque converter is the fluid coupling device that connects the engine to the transmission. Torque converters are built with a certain ammount of slip so that the car can idle with the transmission internals not turning. The slippage is set by the manufacturer to provide good idle and fuel economy in mind. Therefore they have a very limited slip. That would be the engine rpm reading you'd get if you had the car in Drive, both feet firmly planted on the pedals and pushed down as hard as you could. Depending on how good your rear brakes are, you should see the engine peak at a certain rpm, generally around 1700rpm. If your rear brakes are not so good, the car will start moving forward once the engine overpowers brakes.

High stall converters:

These are generally aftermarket items that will allow more engine to transmission slippage. Why, you ask? The engine probably makes its peak power (Torque) at some rpm above off-idle, so a higher stall converter lets the engine develop more power with the car sitting still, thereby giving you quicker acceleration from a standing start. The price for this 'free power' is more slippage between engine and tranny RPMs so you are kissing some gas mileage goodbye.

A good case in point are my 73 Cougars. Both have factory 351C-4Vs. The problem with the low compression 351C-4Vs is that the intake ports are HUGE, and this creates a low intake velocity, making accelleration sluggish. Ford compensated for the sluggishness by installing a higher stall torque converter in the 4V equipped cars. Intead of 1700rpm, this special high stall converter has a stall speed of about 2700rpm, allowing the engine to get into its power band quicker.

Aftermarket high stall converters come in a varied array of stall speeds. A mild stall speed increase will be 2000rpm, then on upwards to the full-out race converters that can stall at 4500rpm or more. Generally, for a mild streetable car, stick with a stall speed below 3000rpm. Street/strip usages are best set at 3000-4000 rpm and race converters upwards from there.

One note of caution. Slippage causes heat. Therefore if you are thinking about running a higher than stock stall converter, be nice to your transmission and add to your transmission cooling capacity by adding an additional trans cooler.

Hope this helps you

Milo
 

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for a potent street car (built with the right parts), the usual stall speed is between 2200-2500rpm.
 
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