Hello everyone, I have a 69 deville that I just changed the power booster and master cylinder on. Is there supposed to be a seal in between these? I have heard both yes and no. I was told my pedal got harder because I didn't put a seal in there.
Thank you for any help. Mike

 

No real seal, a gasket maybe. Hard pedal feel is a good thing, it means that your hydraulics are in order. If, however a hard pedal means that you have lost power (vacuum) assist and you have to "stand" on it to stop the car, then you have a vacuum problem in and around your booster.