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Sorry I tried searching this subject but came up with nothing.

Ok from how I understand it, if I have a transmission with a 3500 torque converter this means that the engine will rev to 3500 rpm until it starts to grab, and make the vehicle move. Is this true? That just doesn't seem right to me because if you was to do this with a manual tranny you would be smoking clutches all the time. Can someone please clear this up, and maybe add some tips on how to choose a torque converter stall speed?
 

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No, the 3,500 refers to the point that the brakes cannot hold the car against the turning of the motor. A torque converter is like one fan blowing on another to turn it. The closer together the sooner the 2nd fan starts to turn (low stall speed). A smaller fan held further away delays the start of the turning of the 2nd fan (higher stall speed). Now at some point the 2nd fan starts turning almost as fast as the first one, but there will always be some slippage. (Driveshaft at 1:1 will be turning slower than the motor.) If you bring the fans close enough together that the blades touch and "lock" you have a lockup situation and the motor and driveshaft turn at the same speed. (Lockup converter)

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Redrum (or Mike)
68 Corvette - 383 CI 427 HP
69 SS Chevelle being updated to Pro-Touring
97 Z-28
 

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Stall speed is the speed at which the converter will theoretically stop the engine rpm from increasing further against a car with the brakes locked.

It's theoretical because the tires will usually break loose before stall speed is reached.

At speeds lower than "stall speed", the converter acts as more of a torque multiplier giving even more power to the rear wheels. It's almost like having dozens of lower gears climbing smoothly in front of the transmission before stall speed is reached.

As cam durations get longer (and "lopier"), low end torque is sacrificed for higher end power. With a stock converter, a heavy car, and a long duration cam, you won't have enough power to get you going from a dead stop.

So a higher stall converter will give you back the low end torque that you lose when going with a longer duration cam.

I'm sure there's more to add to this. I'll let others chime in.



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