[Bob Bidonde]

The dynamometer figures that follow where cherry-picked from the internet some time ago, and I did not make note of their sources. The figures are at the flywheel, and running with modern gasoline. From my notebook:
4.2:1 Compression Stock Head: 38 HP & 130 labs-ft Torque;
5.5:1 Current Hi-Compression Head: 47 HP & 141 lbs-ft Torque;
6:1 Current Hi-Compression Head. 58 HP & 146 lbs-ft Torque.


The best bang for the buck is the currently available 6:1 compression cylinder head.


If you have later / more accurate figures, please post them.