brady5885

So im soon about to get my restoration on the road.

The brakes didnt feel strong so i bled them, and bench bled the master cylinder, i now have a firmer pedal with about 1-1.5 inch of movement on the pedal
(where before it would go to the floor with about 5inch of mmovement).

But stopping power is far from what id expect, i cant even lock them up with alot of pressure.

I turned off the engine pumped it a few times and it didnt get firmer of softer.
I held the pedal down with a little pressure and started the engine and it didnt sink any futher, i checked my power booster with a vac gauge and it held approx 12in hg for a while. and when i press the brake with the gauge still attached it drops to 0 immediately.
I do have vacuum going into the booster, and the one way valve is working as it should.

Any ideas?

SIXFOOTER

Bad booster most likely. Mide did the same thing when I got it. It would stop with a lot of pedal pressure but it took a while. If you stood on it it would stop a lil quicker but it was scary. Put in a new booster and refilled and bled and it would lock up like new.

SuperBuickGuy

sounds like a bad booster (what he said above )

they are a pain to get out, they bolt to the car from the inside of the cabin

brady5885

It is a new brake booster :/

brady5885

Its a new booster, and it holds vacuum overnight = that proves its functioning?

brady5885

m thinking that the valve that controls the air between the two chambers is faulty as vacuum is lost instantly as soon as the pedal is pressed, thus letting atmospheric air into the vacuum chamber???

Would i be right in assuming this is whats happening?

GDaina

Seems that most of the brake issues on this site deal with Power Brakes...am I wrong?

noonie

Probably.
See how much vacuum your engine produces. Anything lower than ~18" will give a proportionally harder pedal.

Here is a simple test.
http://www.mpbrakes.com/uploads/docu...tertestpdf.pdf

brady5885

Ok so i hooked up the gauge, and im only pulling 10in.... but it is fluctuating very fast between 8 and 12.

i have a .488 cam, if that makes any difference to such a low reading

Bagmup

Hold the engine at a steady 3000 rpm and see if the needle still bounces around like that. It may indicate weak valve springs.

brady5885

I had a steady reading even though it was low @ 10in just before i put bigger jets in the carb.
The engine has new springs, and less than 10-20 miles on them.