PAT i thought that the carbs would have good vacuum since im not trying to go off the manifold ill check into that bds valve.The only vac i need is for the brake booster. DO you run vacuum advance on your blown motors i viewed your photo gallery and seen that blower you were talking about its the only single carbed and serpinteen belted one there that is a nice looking piece for shure 'How faroff will it be from a 6-71 in terms of power everything else the same cam, carbs; comp ratio