I have copied a republished them below, just click on the blue/green buttons.
My conclusion remarks to the test are:-
CID = Torque.
While making peak torque at a high RPM will increase the maximum number, the average is generally the same.
Older technology factory heads would make 1lbs/ft per CID, thus a stock 350cid would make 350Tq.
These better LS factory LS heads made peak Tq (torque)517 or 1.26Tq/cid (per cubic inch displacement) whereas the best performing aftermarket head made 563Tq or 1.38Tq/cid.
The lowest number was 542Tq or 1.32Tq/cid. This reveals that better aftermarket heads are all very close in improving power output.
The average Tq numbers show that the peak Tq number is more a result of peak airflow.
The factory head had a port size of 205cc and max flow In of 244cfm.
The best head was 257cc flowing 352cfm, so this proves additional airflow will increase power output.
The average Tq number shows that at lower RPM the engine only pulls in as much air as the cylinder can and even the stock head can provide what is needed..
At 3000RPM all the heads were making between 440Tq to 450. The lower number is often a result of slow velocity of intake airflow due to the larger port, but not always, compare AFR to Black Label.
The average for the stock heads were low because the peak was low, but the best to last aftermarket average was only 11Tq difference.
There my advice, buy the best performing head you can afford, but if it is the lowest cost head, you will still make similar power.