Originally Posted by tweekd

Just to add, the 8 inch converter will bring a small block or small big block under 850 HP to a high stall that it requires. If you put more than 850 HP to an 8 inch your just going to drive though it. The 9 inch converter is useful to a big block running 900 Hp to about 1350 HP. Anything after that is the territory of a 10 inch or 10.5.

In other words, the bigger the diameter the hungry it will be for power to get it moving.