how much better will a car 60' be between a 2.0 str & a 2.5 assuming everything else is the same? will that .5 make a big difference?

Is this how torque is multiplied?
car's torque is 300 -
1.8 str = 540 tq stock
2.0 str = 600 tq
2.5 str = 750 tq
Is this how much torque is applied when launching?

 

STR is kinda not relivent... as soon as you spin even a little tiny bit, your STR goes down to 0.
go to fuddleracing.com, they have a good write of everything you want to know about a converter.

 

Some what correct
but as you brake torque to a higher RPM your engine torque goes up but the STR goes down!! (a 3500 stall converter rated at 2.0 STR might be rated at 1500 or 3000 RPM brake stall)
so that is why each converter, car and engine has a SWEET spot
Yank converters are STR rated at the point that we have tested them to perform best in the style and vehicle the converter is sold for
We are the only converter co. that has the testing for this.
and feel it is best to give the customer the info they need.

 

Depends if you are talking about torque applied to the transmission or the ground...

To make it to the ground, the power is first mutiplied a few times...your power output at the RPM your engine is spinning, converter's STR (at a stop), your first gear (3.06 in the 4L60E) and your rear gear ratio. After figuring in the frictional losses THAT is the rough number of lb-ft of torque that your tires must handle.