[Red Barron]

Is there a generally accepted set-up for measuring a cylinder heads flow rate? Manifold on or off? Header pipe on or off? Flow at 28 or 10 inches of water?… Etcetera.

 

[springer-]

Thats just part of the problem. Now throw into the mix air temp, humidity, barametric pressure and you have the reason head flow numbers are completely subjective.