I removed the brake booster on my '63 to refinish it. After reinstalling,the brake pedal goes to the floor by itself when the car is started,locking up the brakes. After shutting the car off, the pedal comes back up and the car rolls fine when it is pushed. There were no prior problems,all openings on the booster were taped up when painting,and no degreaser/solvent was used to prep it. Any ideas??

There is an internal plunger/valve that closes when pressure is applied to the pedal and thus gives vacuum assit to apply the brakes. That appears to be either stuck or there may be a problem with the pushrod and/or it's adjustment (between the pedal arm and the booster). Is there any free travel with the pedal in the fully released position? The push rod may not be properly seated in the booster.

Thanks for your quick reply!! I just checked the free travel-about 1/2 inch. Without the engine running the brakes operate as normal. Guess a new booster is in order. Thanks again!