Hello all, Pleasse
I have a 1989 Firebird. I installed the baer brakes on the rear. The car brakes great, however I really dont like that prop. Valve. I read somewhere that I can buy a GM master cylinder that was made for 4 wheel disc brakes. Does anybody have the GM part number for this MC. Any information will be greatly appreicated.

Brad

 

Come on , somebody please help me

 

Visit http://www.expressautoparts.com or http://www.carparts.com or http://www.partsamerica.com and you can look it up yourself; best bet would be to go with a rebuilt unit for only $20 instead of $200 from GM. Skip on paying the core fee (usually $20) and then you can keep your original.

Bleeding those suckers is a bitch, though. They use metric fittigns so chances are the "free" m/c bench bleeding kit that comes with the m/c won't fit the ports and will suck air. We also have a quick-take-up valve in our m/c body (feel for it's bulge at the base of the m/c where the bottom of the m/c goes into the brake booster) that likes to keep air inside itself.

 

Is there a year / model that will fit my car. my orginal setup was disc/drum. Now I have disc/disc. If I knew what car GM made that had 4 wheel disc and the Master Cylinder would fit my car then I would order that MC. Any suggestions

 

90-92 f-bodies used the same master cylinder (RPO code = J50) for disc/drum and 4-wheel-disc.

84-89 disc/drum used J50 master cylinder.
84-89 4-wheel-disc used J65 master cylinder.

The J65 master cylinder has a larger bore (25.5 mm instead of 24mm) which allows for a harder pedal "feel" for the driver. If someone uses a J50 m/c on a 4-wheel-disc car, it'll be fine. In fact, Apeiron (on thirdgen.org) dug up a GM bulletin saying that a technician could install a J50 on a disc/disc car if the owner complained that they were too weak to push the brake pedal. Some people shouldn't drive sporty cars...

So actually, I would say not to replace the master cylinder; it might not help. What prop valve are you using?

[edit] Notice I left 82-83 out of the mix... they used the J50 and J65, but they use standard threads- GM used all metric threads for 84-up, so you definately wouldn't want an 82-83.

 

Tom,
The J-50 master cylinder is the factory installed on my car. I have
the Baer disc kit installed on the back and a have a baer prop valve intstalled for the rear brakes, I removed the stock prop valve. The prop valve is almost fully pressure adjusted in the rear, it seems to me the rear should be brakeing more. Any suggestions.

 

Tom,

That's some good information there. Thank you

 

Stick with the J50 master cylinder. That's what the 1LE cars used and as Tom mentioned, GM used the J50 on all models from 90-92. My '88 disc/disc car has a J50 mc even though according to GM's original specs it should have a J65.

More than likely if you get a rebuilt unit at Pep Boys or wherever, they'll give you a J50 unit. As far as the rear brake bias, if you have the pressure dialed in heavy for the rear brakes they should be kicking in pretty hard.

What specifically is the car doing or how is it behaving? A little more info. could be helpful.

 

Well, I installed the bear disc in the system removed the stock the Prop Valve line going to rear brakes and installed the baer brake Prop Valve. I have the prop valve almost fully CW and it appears to me that the rear brakes should be brakeing alot more. I see very little pad dust. I am thinking about getting a prop valve for a 4 disc brake gm. Any ideas on what I should try/do

Brad