We have learned that BTU's and Octane have no noticeable effect on performance. But I have learned that Octane allows you to make improvements to the engine that will increase performance. For example the Sherman high compression head on my 9N. In this video you can hear a very nasty spark knock and the end of my run. I had to upgrade to 93 octane gas and retard the timing 4 degrees to make it stop.
Seem to have a problem getting the video to post?