:confused: Here is the problem, I purchased a reman. booster/master cylinder combo. It all comes together. Sometimes when I stop I have really good power assist, other times it feels like the good ol' manual brakes. When I pull out the check valve from the booster there is plenty of vacuum. I don't here a leak anywhere. Could I possibly have a bad booster/master cylinder? Should I look elsewhere for the problem? The only thing I did not replace is the proportioning valve when I did the drum/disk conversion. Please help, I am going crazy! :clonk:

stock motor?
making lots a vacuum?

david

It is not factory, but a stock small block chevy. It is making plenty of vacuum. When at idle and I unplug the check valve, there is tons of vacuum.

My car does the same thing especially at low speeds on a slight downhill incline. When I had brand new "A" body cars they all did that too. A 68 Hurst/Olds and a 70 LS6. Both with power disc brakes.

My guess is that a slightly smaller master cylinder piston would help. You need something to give you more FT/LBS force on your brakes.

The hard part will be finding such a part.

I have a feeling someone could make a killing rebushing master cylinders for old cars who's brakes are inadequate due to having remanufactured master cylinders. IE:Master cylinders that have been bored out to get rid of internal damage. Bored out means less work done for a given amount of pedal pressure.

Might want to actually measure the vaccum with a gauge. They're cheap and have many uses.

There is a vent around the housing on the pedal side of the booster. It should be open so that air can move in and out as the diaphragm moves. A noticable whooshing sound can be heard inside the car when the brakes are applied and released. If carpet or insulation cover the vent it can cause a hard pedal.