Hey everyone,

I’ve been restoring my 1988 Firebird Trans Am GTA (5.7L, front and rear disc brakes) and I’m close to getting it road-ready. Recently I ran into issues with the proportioning valve -- I had a refurbished 5-port unit installed (two to MC, one to rear, one to front left, one to front right), but one of the ports stripped. Replacement 5-port valves are getting hard to find and are very expensive.

Here’s my idea:
What if I use a more commonly available and more economic 4-port disc/disc proportioning valve and just add a T-fitting immediately after the front output to split the pressure between the driver and passenger side front brakes? Has anyone done this? Would it create any problems with brake balance, pressure differences, or safety?

I know the OEM design had separate front outputs for redundancy, but I’d love to hear if people have run a setup like this successfully -- or if there are important reasons to avoid it.

Thanks in advance — this forum has been a lifesaver for me during this project.

Here is an example of the 5-port I have now. Two on the top run to the MC, the third and the two on the bottom run to the calipers.

This is an example of an OEM 4-port proportioning valve. It only has one port on the bottom.

 

 

They both have 5 ports

2 inlet
2 front output
1 rear


Either of the front outlets can be plugged and teed later
Not sure how you're going to plug a stripped hole