Torque converters

[burt ragio]

If two converters had the same stall speed one a 9” the other a10.5” what is the difference ?

[Turbov6Bryan]

that 9 inch will not be a lock up, if it is a lock up, it has less surface area for the lock up disc- if your tune is set to lock the converter in 3rd gear, it will wear out the lock up disc soon, and then the converter is less efficient than a 9 inch WITHOUT a lock up.- because the disc will slip, setting the inefficiency higher than if it wasnt a lock up.
the 10.5 could be a lock up, most likely a singe disc. If its a multiple disc lock up, you can shake the converter and hear the multiple discs rattle in the converter.

Picking a converter- if you choose a lock up style- it will only be most efficient while locked up, a really really good non lock up converter can be designed to have less slip, or very equal to amount of slip of a lock up while being locked up-
the point is picking a efficient converter- i know dusty bradford was hot and heavy making the pats ptc hughs non locks as efficient as a 5 disc vigilanty converter...

now if you just want a higher stall speed and cars not really raced much- marty sells a good convertor-
the 9 inch convertor since its 15 pounds less, might need a idle tune change- car might not idle well--