I have a '39 Chev Fatman frame with power disc/drum brakes. I took it for its maiden voyage today and found that I had to stand on the brakes just to get it to stop. According to Fatman they use metering valves for their disc/drum applications......a 2psi residual pressure valve between the master cylinder and discs and 10psi residual pressure valve for the drums. I've pumped the brakes while the engine was off and started the car. The pedal went down ever so slightly (obviously the booster is working). The engine is a stock 350 and the 7" dual power booster gets its vacuum from the intake manifold behind the carb. What am I missing that's causing this condition?