Only If You Have An Automatic Transmission
P._. - What is a stall or torque converter? Why would I want to use one in my 1967 with a 396?
B.S. - There has to be some way for the power (rotational torque) to get from the output of your engine (the back of the crankshaft) through the drive shaft to the rear axle and to the wheels of your car so you can go somewhere. If cars had only one forward gear, this would be simple, the flange on the crankshaft could be bolted directly to the drive shaft, go into the axle, and turn the wheels. However, since cars need more than one gear to operate properly, they need a transmission that allows the driver to shift gears and attain faster road speeds at the same engine speed. You need some way to make and break the connection between the engine crankshaft and the drive shaft, so you stick a transmission in between the two. On a manual transmission car, the connection is broken and remade by the driver each time he puts in the clutch and lets it back out after shifting gears. The clutch makes the connection between the crankshaft and drive shaft using friction plates that hold tight without slipping when the driver lets the clutch out. An automatic transmission is a different story all together. The driver never has to manually break this connection to shift because the automatic transmission does it for him with the torque converter. The torque converter is nothing more than a fluid coupler that connects the engine crankshaft to the drive shaft using hydraulic fluid (transmission fluid). There is no direct mechanical connection between the crankshaft and the drive shaft in an automatic transmission. This fluid coupling method allows the transmission to shift gears automatically and without breaking any mechanical connection. It does this by monitoring transmission fluid pressures and/or engine vacuum (depending on the transmission). So, why do you need one? Your automatic transmission will not work without one. Every automatic transmission has one.
F._. - Pick up a copy of Chevy Hi Performance for October it will tell you every thing you need to know about converters.
S._. - There is no such thing as a "stall converter". All torque converters stall; it is the nature of the beast. The RPM the converter stalls at can be varied by any number of methods. Chief among them is the diameter of the converter or the pitch of the stator vanes. A converter that stalls at a higher RPM than the typical "stock" unit could be called a high stall converter. Stall speed varies with engine torque, so a 4000 RPM converter behind a 502 might provide a 1700 RPM stall behind a 283. Advantages of a higher stall converter include: More torque multiplication which means better acceleration. An engine that is set up with a high RPM cam produces poor low speed torque and usually idles at a higher than normal speed. A higher stall converter slips more at idle speeds and eliminates idle creep along with allowing the engine to wind up into its power band when launching. A high stall converter is usually smaller and lighter, producing less flywheel effect and faster RPM gain. In short, your engine will idle easier and rev quicker. Disadvantages include heat. High stall converters are less efficient at transmitting power and the wasted energy turns up as heat. You can expect your fuel mileage to go down especially in town. General Motors had the big fix to the problem back in the mid sixties, then abandoned it because it cost too much. Some cars were equipped with a "switch pitch" converter in which the stator vanes could change pitch to provide more torque multiplication when accelerating and then change back to provide good efficiency during cruise. freely.
Archivist: Tom Wilson
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