Sticking that squared-off chunk of metal up into the combustion chamber probably plays havoc with the flame front as it tries to get from one side of the chamber to the other. I'll bet that engine would be very prone to developing some destructive detonation, and that much static compression would only be required with an extremely radical camshaft grind.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!