I am not sure I understand correctly what you mean.
I guess you're asking about a SOHC which actuates 4 valves / cylinder, out of two cams per cylinder - one actuating both intake valves and the other both exhaust valves.
For example, something like this:
http://upload.wikimedia.org/wikipedi..._Cylinders.JPG
but with one single intake cam replacing a cluster of two cams.
Or you meant something else?
Later edit:
Many years ago I visited the Deutches Museum in Munchen, Germany. I remember that I was bemused by the Daimler Benz DB 601/605 engine, which was used on some German WWII aircrafts. It had an odd valvetrain setup, with a single camshaft actuating 2 intake and 2 exhaust vales per cylinder, out of just 2 cams. I guess this engine may be closer to what you're looking for.
Here are some links:
www.aviation-history.com/engines/db605.htm
upload.wikimedia.org/wikipedia/commons/6/6c/Daimler_DB_605_cutaway.jpg
Maybe you can find somewhere else on the Web larger pictures of this engine.