Vacuum Secondaries

Smaller carbs will run ok thats a fact, its down to what you prefer, your level of skill in tuning a bigger carb and just what you are happy with from your combo and what you want it to do and how/where you do it. I can only give my actual experiences from the street and the results from the track and I for 1 would not want to drive a 340 around with a 600VS and have the car be a slug, thats why they came from the factory with an 800 thermo....and I ran 1 of those as well for a short time....nothing could touch the 850DP for shear power low down and up top and if tuned right its good as gold on the street. If all your doing is getting groceries with your car, then yes run a 600.