Small cube big bore short stroke motors today that spin 10-11K can fairly easily make 3-3.2+ Hp cube. I generally believe the short stroke allows for more of an RPM spread between peak torque and peak HP.

As with any other piston engine, after maximum VE (torque) RPM is achieved the bottom end acts like a friction brake trying to slow the crank.

What's really impressive to me are those Australian CHI Ford Cleveland heads some of the Aussie pro stockers run.... they are super impressive and make very similar HP/cube as our 500" NHRA pro stockers.

I'm thinking the unrestricted NASCAR motors are getting up near there too now, plus they have to live for 500-600 miles!