Stall Speed different from sb to BB?

[johnathan]

''Stall speed is measured at wide open throttle. Anything less than WOT will have a lower stall speed. Our 700R4 torque converters lock-up in overdrive automatically. For street use in a 2WD (under 450 horse power) you would need somewhere between 1800 to 2300 stall depending on what feel you like. A 4WD for street use usually uses 1600 to 2000 RPM. Higher stalls than these are usually used on higher horse power motors and for drag racing. The ratings you see on torque converters are for small block motors. The same converter behind a big block will stall as much as 700 RPM higher. A 2800 or higher stall speed on the street would have a jack rabbit take off at full throttle, but have a mushy feeling at less than full throttle. The higher the stall speed the softer the shift feel.''

How can a torque stall more behind the BB. I thought the stall speed would stay the same.

 

[Amtek]

Engine torque at lower RPMs vary between SBC and BBC. A BBC is obviously gonna have more torque so the TC is gonna slip a little more and have a higher flash stall speed.

TC stall speeds vary greatly between vehicles. It depends on the engine, the gear ratio, the tires, and the weight of the vehicle. For example, I have a 350 SBC with 3.73 gears on 37" tires. I have a TC rated at 1700-2100 RPM. With these gears and tires, my stall speed is 1900 RPM before I launch. If i swapped the 350 with a 454, The stall speed would probably hit 2100-2300 as I launch from a stop. If i replaced the 3.73 gears with 4.56 it would probably only hit 1900-2100 before it launched because it would be easier to turn the tires.

 

[johnathan]

I see