Poor brake pedal
I have a 1967 Camaro that hasdrum/drum brakes and a brake booster. Ihave very little brake pedal…almost to the floor. I have installed and bench bled a new mastercylinder, new wheel cylinders, new shoes and new drums. The brakes have been bled many times.
Before I start the engine,i.e., no vacuum in the booster, I seemto have a decent pedal but that pedal drops significantly when the engine isstarted. It seems that what decentpedal I had goes away whenever the booster is on.
My booster vacuum runsdirectly off the manifold and seems to have good vacuum. With the engine not running, I depressedthe brake pedal several times to remove any vacuum from inside the booster. Ithen held the brake pedal down with some pressure and started the engine. Immediately the pedal dropped slightly.
It seems that whenever thebooster has vacuum the brakes are very poor and when the booster does not havevacuum the brakes are not the greatest but much better.