Tom,

Yep, that's a turned down stem.

Also, see how there are only two angles on the valve head? A backcut would add one or perhaps two more shallower angles where the valve seat surface meets the back of the valve. Right now there's a pretty sharp lip there, and it can disrupt the airflow. Making a couple of angles leading into the valve seat surface keeps the flow attached and increases airflow significantly.

MC

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Mark Coffin
#14 GP BSI Racing/Airborn Coatings/The Shop VW
Scirocco
Zephyr Race Coaching and Consulting
http://pages.prodigy.net/Scirocco14gp