Here's the combustion chamber of the modified 2.2 head. It has been slightly unshrouded for improved airflow, and has been machined to fit 1.94" intake and 1.625" exhaust valves. Stock valves on the 2.2 are 1.77" intake and 1.57" exhaust. Airflow has been improved 21% (intake port) over that of a stock 2.2 head. Intake port airflow is a whopping 66% more than a stock 1.9 head's intake port.