What size torque converter
 

What determines the size of a torque converter, i.e. 8,9,10 inch that should be used?

MOTOR,CAM,REAR GEAR WHAT YOU WANT TO DO WITH CAR,ETC,ETC....IM SURE THERE'S MORE.

Let me modify the question - What is the difference then between all these converters that would lead one to to choose one over the other. They all do the same thing.

lots of differences
 

If you are using a Nancy small block and want say 6000RPM stall then a 8" will likely be the best base to set at that stall.
If you have a big inch man motor and want the same stall of 6000 lets say, then a 9.5" to maybe a 10" may be the best to set up for that stall. The larger converter diameter will be easier to lock up and harness a big block in top gear. The smaller diameter will have the same effect on the less powerful mouse motor and free up some power with the smaller diameter (less inertia to rev up). The big motor will rev thru the 8" in top gear and not have enough holding power for the greater power level, generally speaking.
Each manufacturer has there own stator turbine set ups that they interchange to get a specific stall with a given diameter. So the answer will be ultimately the torque converter builders perf for your power level, car weight, gear ratio, etc.........
Does that help?
Bruce

Nancy?.......Thats harsh.

Yes - That helped. Thanks.

Re: lots of differences
 

I think on our application that is what is happening. We didn't change the convertor and had an injected small block, and put a blown big block in with the same convertor (8") and the motor is on the rev limiter way early and we have been thinking it was the mag but I had been thinking it was slipping throught the convertor. Sorry didn't mean to jack the thread.
Rick

Re: lots of differences
 

Rick, You are likely correct. I have used 8" converters on my 500 HP oldsmobile small blocks that ran 10.20's in a 3400# chassis but that was about the torque limit on that converter set up. We needed a 9" for our 385" oldsmobile diesel blocks in the same chassis to get them to couple on the big end and still give near the same stall on the line with the larger engine set up. On my 582" with 12 degree heads that makes 1170 raw HP on gasoline, I use a 9.5" coan converter on that one, and it does lock up in third gear about 100' before the 1/8th mile!
Bruce