Installed a SSBC kit on the front of a 72 Custlass. No problems with the install, bled the brakes and bench bled the new MC. Went for a drive to bed the pads in. Light braking was ok and seamed to improve after a few stops,however if you try to stop quickly, you have a hard petal with poor braking. Bled the brakes again,manually and vacuum bled. No change. Installed a new booster, no change,installed a second MC ,no Change.
Checked the preasure at both front and rear 1000-1100 max. (no perporsioning valve yet) Vacuum is low 12" at idle,but does go up to 18" at cruise, vacuum line and check valve are good.
Car sat for afew months, now back to work on the problem, sanded the pads to remove any glazzing. Checked for proper wheel cylinder operation in the rear, OK.

ideas?

 

I would think you are fighting a losing battle without the proportioning valve installed. In order for the brakes to "lock up" appropriately the pressure has to be "proportioned" between f & r.

 

I expected without a perporsioning valve to have the rear wheels lock up first on hard braking. With a 1000 lbs of hydraulic pressure avialable when checked on the lift ,I would of thought the rears would skidding with any quick stop. They do not. I am test driving the car on a two lane, tar chip country road. If I was on traction groved concrete, I would expect a harder time of skidding the tires. (new BFG's)

 

The way I understand it, without some help the rears will not work much at all. As I have heard, when Olds first put front disc and rear drums, they used a "hold off valve" which kept the fronts from getting pressure until the rears got enough pressure to overcome the springs and get the shoes close to the drums,, remember the pads are always in contact with the disc. Then they started using a proportioning valve which did the same thing but is all one piece, prop valve and distribution block/junction block for the lines.
I did the front disc swap on the 66. I got the factory replacement parts, correct master cylinder, hold off valve and distribution block and lines from In-line tube for the 67 Cutlass. The rest is just generic "A" body swap parts. So far it is working very well.

Mike

 

Thanks for the replys

The guy that is helping me install this is a Mopar guy, so he is not up to speed on some of the Oldsmobile details. He has done a few kits before and the disk brakes on his Chargers work well. An other Buddy , Chevy guy , is stumped also. Trying to get some help from SSBC.

Will try the perporsioning/metering valve, suprised it did not come in the kit, with the MC. Any recomendations on where to get one?

 

I would think the 12 inches of vacuum is the problem.
Nephew had the same problem, until he changed motors with 15 inches.
Stops fine, now.

 

Ding, ding, ding...

We have a winner.

 

Installed a vacuum pump. Drove with 24" vacuum at the booster. No change.
Checked the brake petal lever hole ,as suggested ,only one hole.