The best way to test the flow of a cylinder head is on a motor dyno. The next best way is a chassis dyno. Both of these tests are real world tests. The easiest test is using a flow bench. This test is not as accurate as a dyno because many assumptions are made (air is steady state flow in a bench, air is much lower pressure, etc). The flow bench is a quick test of relative flow in each port at different valve lifts. On the following tests only one cylinder was flowed. This is quicker (cheaper) but for complete testing all ports should be tested. A Chevy head was included to give a baseline of a modern production high performance head. This head is unported.
Note that the Stock and Power Heads are Turbo castings. The head Allan ported is a NA head with big exhaust valves. The Power Heads use backcut valves. Allan's valves are stock intake and as delivered exhaust.
The 2.3L head was tested at Power Heads, 25in Hg pressure.