Sorry, I typed the wrong number, should have been 4C, not 5C. Even with the small amount of seat leakage (which doesn't matter once the valve is open) and the guide leakage (which might but is very minor), the results are pretty consistent. The authors suggest that the numbers be used for comparisons between different heads but dyno tests would be even more informative.
The 1.77 exhaust valve heads on average flow about 18% better than the 1.66 valve heads - on the exhaust of course.
