I bought a BG 750 Speed Demon VS carburetor last year. Based on all the comments floating around, I took it apart to inspect the internals. The inside was spotless. Reassembled and installed on my 71 Roadrunner. With the four corner idle and the idle-eze feature, this carburetor ran great. Only knock I have is the choke system has only gravity to pull the choke butterfly open. Holley uses a piston inside the choke housing to force open ( a better design in my opinion). The BG choke system causes too much gas to be pulled from the venturies and runs extremely rich during the first 30 seconds on the choke. The only work around was to adjust the choke housing to the extremely lean side. Once warm, no further problem.
Ron