I converted the front drums on my 68 Chevelle to 1969 discs. Everything is rebuilt or new. I bought what is supposed to be the correct master cyl. and prop.valve. It is not a power brake car. The pedal has always felt spongy no matter how many times I bleed the system. I also have new rubber lines. The master cyl doesnt look much different than my drum brake unit. I looked at a buddy's car and his master cyl is larger than mine, but its a power brake car. The car stops better at hi speed but worse at low speeds than my drums did. The spongy pedal takes more travel so response time is slower and it takes more pedal effort now. Also harder to hold the car still in the staging beams. It seems to be getting worse and feels like air in the lines, but bleeding doesnt let any out. Any help would be very welcome.