Hard brake pedal

I replaced the power booster on my 69 coronet, due to the original diaphragm leaking. Car was originally power drum.
The disc conversion worked great up to the original booster failing, with the new booster installed the pedal is very stiff, and requires a lot of effort to stop, where little was required before.
Any help or ideas?


m/c and proportioning valve are off a 79 newport, spindles and calipers off 76 aspen.

If you have very hard pedal and very little travel
I would say your booster isnt working

What P said as the only change from good to bad was the (needed) booster swap. I would check the pushrod free play when you seperate the M/C and booster