No worries on that, trans and converter operation/function can be a black box for folks beyond just a basic understanding of how those things work.
The main factors to consider when choosing a stall speed if going with something other than stock, including but not always limited to:
1) cam grind (specifically lift/duration) - call your cam manufacturer as they will provide recommendations for stall speed range
2) final drive ratio (your front/rear diff ratio)
3) Vehicle weight and tire diameter (thanks, @iamdub !)
4) Vehicle application (towing, hauling vehicles, converter stalls will be much lower than stall speeds used in racing/street strip applications as an example)
Converter performs two primary functions:
a) torque multiplier
b) fluid coupler
High level explanation: The converter acts primarily as a torque multiplier earlier on in the RPM curve then at a given rpm speed it will achieve full fluid coupling with the engine. This rpm speed is the converter’s stall speed. The higher the stall, the more torque multiplication occurs before fluid coupling, hence the more overall engine torque is able to be utilized, all other things equal.
Related tidbit: Back in the day, the act of converter achiving full coupling was referred to as “lock up” however this should not to be confused with the term “lock up” used when discussing converters designed with a clutch today as those weren’t in widespread use until the 80s.
Im out of town atm but sometime after I get back, I will probably do a video explaining converter function, show the parts inside a converter that determine stall speed, what info to use when trying to determine optimal stall speed range in relation to the rest of the factors mentioned above.
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