I just recently purchased a 1984 Camaro that has a 91 z28 rear end with disk brakes. The previous owner did not change the proportioning valve and said the car seem to stop better with the drum brakes.

After doing some research on this board I know I have to change the valve. Right now it seems like the most common fix is to eliminate the stock valve and install a Willwood adjustable unit for the rear brakes.

After finding this link, http://www.ws6transam.org/1LEbrake.html#1LEfront , I think there might be an easier way. Can the stock valve be replaced with a stock valve from a rear disk car? The article even gives the part number as 14089496. The article stated that if the car had rear drums then the master cylinder does not need changed which would lead me to believe this prop valve would be a 'bolt-in' part requiring no cutting or flaring of brake lines.

What do you think?

 

I would think that should work. I'm in the process of swapping an '84 Trans Am posi rear-disc rearend into my '85 drum rear Camaro. I just undid all the lines to the stock prop valve on the donor car and took the valve. It looks identical externally to my Z-28's Drum valve, but maybe the part number is different. The lines all go in the same places though, so it should just screw into place! I'd find the stock one for that '91 rear disc and use it. That's probably why the rear brakes don't work on yours now, there isn't enough line pressure to operate the calipers correctly.

 

Knight Warrior: If I'm not mistaken, I believe you will also need to swap the master cylinder on yours. I did alot of comparing GM part numbers trying to figure out which valve to use and found the pre 89 disk brake cars used a different master cylinder (the post 89 disk brake cars used the same master cylinder as the pre 89 drum cars, doesn't make a lot of sense but its true).

I decided to go with the wilwood adjustable unit on mine. I picked one up from a guy over at frrax.com for $20. That beats the $108 that GM wanted for a 91 prop valve which may or may not have worked correctly.

 

Oh crap, good to know. Looks like I'll need another trip to the wrecking yard!!