If I'm digging through a bin full of Corvair H (primary) carbs. How do I tell which ones have power valves? Most of them don't have tags. I've always taken them apart in the past, in order to find out, so I don't know how to tell from an external-only inspection. Thanks Andy Clark 66 140/4 Monza Sedan 66 140/4 Stinger Clone 66 180/4 Cord 8/10