Doesn't a cylinder head which flows enough to deliver 80 BHP, have enlarged inlet ports and is designed to operate at very high revs ? If that is the case, the bottom end of the motor needs to be a lot stronger, and preferably the crank would short stroke, so that it spins up higher without creating extreme loads. I suspect that what you get on a flow bench, often is not an indication of what the port will do when it is operating in a motor. You are measuring gas speed through the port at sustained pressure, not when the gas in the port is resonating at the speed of sound. What someone needs to do is progressively port a head and keep fitting it to a standardised motor and measuring the torque and ultimate horsepower - establish a correlation.
What I have done to the 850 head on my bike, is the result of having made mistakes on my short-stroke 500cc Triumph which have been irreversible, and also observing what works best on Triumph 650 motors. My feeling is that once the inlet ports are enlarged much beyond standard, the gas speed within the port drops, so the mass of gas transferred might actually decrease at certain revs - you lose torque.
