Your description of the valve made me laugh. People come up with some amusing names for things sometimes. You're saying the valve has a little head and a small head. If it's brass then it's a manual valve. If it's plastic it might well be a solenoid operated valve. The wires might be broken off so short you couldn't tell it had wires. Maybe you can find a link online somewhere to a picture of your valve.
http://images.search.yahoo.com/search/images;_ylt=A0oGklJTuFhI_3IBzkZXNyoA?ei=UTF-8&p=rainbird+valve&fr2=tab-web&fr=msgr-buddy