I did a disc brake conversion on my 1930 Ford coupe with '40 Ford spindles. I have a dual master cylinder mounted under the floor. Under normal driving conditions I feel the need to pump the brakes. They do not feel right on the first application of the pedel. I have bled the brakes and installed the residual pressure valves front and rear and have an adjustable proportioning valve for the rear. I believe the problem lies in the fact that the master cylinder is below the calipers in front and can never be bled properly. If I pump the brakes just once, then it feels fine and stops really good.
With that being said, I had an emergency stop on the way to the NSRA nats at Richmond in 2006. A car turned in front of me at an intersection and I locked the brakes up in a panic stop without pumping them. They worked fine although my hotrod was severly damaged.
Bottom line is, I have the car back together now with no change in the brakes and I have to assume they are OK do the the fact that they stopped the car in an emergency as was expected.