Brakes feel like manual on gradual stop.

[84BuickGNYorkPA]

I need some advise, I have a 87 motor, with the vac set-up. And a bunch of new brake parts including master cylinder, brake booster, rear shoes & brass proportioning valve. According to the scanmaster 2.2 I have a -8 value on the boost reading.
Here is the problem, when I first hit the brakes they seem good, but if I ride my brakes gently for say 40 yds while comming up on a red light, by the time I get to the light my brakes feel just like my Dad's 65 Chevy pick-up manual brakes.
My signature is current, I have two questions, first are my low vaccum readings related to my brake problem? And 2nd, what can I do to improve my brakes?
Thanks,

Chuck

 

[BlackMetal]

I don't think you have low vacuum. -8 is probably reading in PSI since it's your "boost" reading. -8 PSI is around -16 in/Hg which is normal for these cars.

 

[84BuickGNYorkPA]

Oh, I didn't know that, thanks for the information....
I have no clue then why my brakes aren't working right, I replaced all the parts except the lines, the rear cylinders where replaced last spring with the S-10 cylinders. I might just have to take the car to a brake shop.

Chuck

 

[84BuickGNYorkPA]

I don't think you have low vacuum. -8 is probably reading in PSI since it's your "boost" reading. -8 PSI is around -16 in/Hg which is normal for these cars.

I installed a vacuum/boost gage tonight and the scanmaster 2.2 is right on the money. I only have 10-8 lbs of vacuum at idle the gage and the scanmaster are identical.

Chuck