So to tie that back into Boblee's question, they make a LOT of torque. This is by nature if their displacement.
The average aircraft motor seems to make between .9 and 1.02 foot-pound per cubic inch if you are to believe their HP ratings and provided these are achieved at 2850 RPM
That's not a lot of torque per cubic inch, but they have a lot of cubic inches. In the automotive world, a 360 is a mid sized V8; A/C does it with a 4 cylinder!
Also, like Jim said, their max HP RPM might not be their max torque RPM, so they could be making more torque per cube at a lower RPM