Brake help, PLEASE!!!!!

[88convert]

I need some help here guys! I had a problem last fall, I had a chunck of steel on the road hit my RR brake line. I replaced the line and decided to go from SVO calipers to GT ones. When I took it for a ride the brake pedal was hard as a rock and required high pedal effort. I was told that I needed to change the SVO M/C to a 95 GT, I did and no change. I replaced the one year old rear calipers, had all the rotors turned, all new pads and no change. There is no prop valve, just an adjustable one on the rear.
I then went to an original M/C.....no change. The only thing left was the booster, and yes, you got it...no change. I hooked up a refrigeration vacuum pump and pulled a 23" vacuum and it still no change.
Yesterday I pulled the M/C, made a gauge and checked the push rod and it is a little too short. From what I have read, if that's the case you should have too much free play. If I'm pulling a vac on it and depress the pedal the vac level drops to zero and will not recover until I let off the pedal. With the M/C on, pedal travel is minimal, with the the M/C off the booster it goes right to the floor.

I am at a loss and need some help! I've got to get it ready for Carlisle. HELP!

By the way, it's an 88LX, 5 lug, 4wheel disc.

Thanks! Ralph

 

[Shakerhood]

Maybe you need the original Gutted prop valve in place with a 3-2 kit.

 

[jrichker]

What disc are you running up front?

 

[88convert]

SVO discs With GT calipers.

Keep in mind, it worked before.

It's hard to believe but it could have a coincidense that the original booster went bad and I got a bad replacement.
I'm still trying to find out if the vacuum level should go to zero when the brake is depressed and not recover until the pedal is free'd up????

 

[Leezure]

I'm working the same problem. I swapped out my OEM booster for a 7 inch dual diphragm booster because of clearance problems with the new engine. To make a three day search short, here's what I found.

The plunger on my booster was making minimal contact with the piston on the Master Cylinder. The booster provided all the assistance I needed and the pedal went all the way to the floor with minimal braking effect. Once the booster has reached the end of its travel there is no vacuum remaining in the booster itself.

I solved this by adjusting the plunger on the booster ( by loosening the screw and tightening down on the nut to keep it in place) to its longest extension. This allowed the booster to provide assistance in moving the piston in the M/C by eliminating the end play instead of having it provide assistance in moving the plunger across the void until it hits the piston.

Hope this helps.