way back about 25 years ago I made the cowl vent on my wifes car open with a rear wiper motor that I got from the junk yard.
can't till you what car it came from, I picked up a bunch of them at the time and used one.
i took it apart and welded a rod to the arm inside and mounted it under the vent.
I had to time it to be closed, but it worked great


or you can try one of these.

http://www.yogisinc.com/index.cfm/page/ptype=product/product_id=9916/prd9916.htm

http://www.hotrodhardware.com/index.cfm/page/ptype=product/product_id=2606/prd2606.htm