I don't recall a quadrajet ever being that small, but I could be wrong. I still think it's throwing your air/fuel ratio way off and running too rich. I have no idea how to tune a quad, so I would say try to find someone with either an Edlebrock 650 or a Holley 650, borrow it, and see what changes. Also see if they can tell you what size your current carb really is. I can look it up by a number on the carb using a Haynes manual. Check the carb and give me all the numbers on it and I'll see what I can come up with. If it works out to be fine by using either one of those carbs, get one. Edlebrocks are great for street use, but if you plan or doing any kind of racing, ever, go with a Holley.