I have everything I need to switch from drums to disc. I have one question. The prop valve on my set up I currently have in my car has the brake line coming in from the front. There looks like the is a port on the bottom unused and plugged up and over the plug is a small rubber cover. Now on the disc prop valve it has that line that goes into the bottom and has a plug in a possible front port also with a small rubber cover. Now is that the same port as the bottom on the disc valve? Can I just unplug the front and plug the bottom so I dont have to try to bend the line? Or is that the difference between the 2 types of valves? Will It work right this way? Has anyone else tryed doing it this way without problems who swapped drums to disc? Thanks for the help.

 

DON'T DO IT!

Don't touch those sealed ports! They're not ports, they're spring loaded valves, with a special sealer on the threads. Well, the ports that you could put a socket on are this type. Ones -completely- covered by a rubber cap (probably at the rear on your disc/drum unit) are a type of pressure-equalization valve.

I had the same situation, but a bit reversed- my '86's disc/drum prop valve had the rear brake line entering from the bottom. The '84's disc/disc prop valve had the rear line enter the front.

The disc/disc valve had a port on the bottom; I thought "Hey, I can unscrew it, and re-use my brake line!" Nope! The spring came out, I put it back together using Loctite instead of a brake-fluid-resistant sealant; the thing was sucking air, I coudln't bleed the brakes, etc etc etc... so don't do it!

What I did finally do was score the correct "enter my valve from the front" rear brake line from a junkyard car... that way, everything fit up, and I didn't have to bend any lines.

GM quoted me $90 for a new prop valve. Maybe you can order a year-specific one for your Firebird (what year is it?), that way you won't have to mess with any lines.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

Thanks!! I would have tryed it if you didn't tell me about it. I like to at least try things to see if it might work unless I know otherwise. Thanks. I will bend my lines because the have almost no corrosion. I may later get the whole line but for now I don't have the time or money. Thanks again!

 

I had the same problem when I did my rear disc conversion and I just put in an entire rear brake line that the wrecking yard gave me for nothing.
The install only took a few minutes with a friends help. The clamps that hold the lines up under the car only go over the fuel lines, the brake line is held in place by bendable tabs and were very easy to disassemble and reassemble.

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'84Z28/'92 305TPI
'92 complete rear suspension/PBR disc/Posi/3:42
Light weight 34.5mm stabilizer bar in front
23mm sta. bar in rear
rear lowered 1" by cutting 1 1/4 coils of '84Z28 springs
comp cam, flowmaster
TB coolantbypass/shutoff valve to heater core
MAT relocated
Ram-Air(home-made) gutted air-box
IROC ground effects/wheels GY245/50's
700R4 superior shift kit/ corvette servo(excellent shift kit btw)

Rebuilt engine and transplanted it myself.

Love this engine!

freshly painted OCT. 2000 bluegreen with two white stripes on the hood and deck lid

LOW performance people should drive low performance vehicles!

 

The correct proportioning valve or combination valve for your disc/disc application is machined from billet aluminum. It does have the 2 lines from the bottom at Tom P describes. That same P.V. was used on 89+ disc/drum cars as well. You should be able to carefully re-bemd the line to fit the new location. But I agree that getting the correct one from a wrecking yard would be better. Good luck, Lon.

 

Thanks, right now I was under my car trying to pull the rear body hoseto rear brake line (the one to the prop valve... dang that thing is rusted!! It started to twist so I stopped before it broke so it looks like I will be searching the junk yard for the right one now. Will be milking my current one and hope it hold up until then. Thanks for the help.. Erik