Rear brake proportioning valve options on 1985 GSL
 

Went thru tech section and it appears that many FB owner don't run this valve. And from talking to other Rotor-heads; many replace with aftermarket. Questions: 1) What is the reduction of brake efficiency (or reduced stopping distance) if not running this valve. 2) What is most common aftermarket valve and how do you have balance set-up. I am having trouble finding OEM replacement (any recommended sources). Thanks.

Replacements are from used sources. I don't think a new one will be found. Not running one will cause brake imbalance on hard stops and possible uneven wear. You should use one. For drum rears this is especially true but for disc I don't know how critical it is.

On my 1979 (drum brakes), there isn't a valve. The line comes from the master to one side of the brake cylinder and out to the other side. Not sure about other drum brake years.

You could probably run a wilwood valve, I have been thinking about running one since I can lock the fronts super easy with my Turbo II brake conversion

My 80 has a proportioning valve hanging off the side of the master which the rear drum lines go through. You need the valve for drums so they maintain a minimum pressure to make them stay slightly out against the drum, otherwise they would rattle around in the drum and not work right. I would think your 79 is missing this but would have had it when new.

I was thinking of the block normally on the rear axle. Yes, I have the one at the firewall.

Freeskier7791,

When you did you T2 brake install, did you do the rear brakes also? If not, that would explain your front lock-up. We did that with our endurance racer and the car lost braking ability (because of the lock-up) and ruined a lot of tires. Installing the T2 (or at least 2nd gen) brakes on the rear solved the problem.

Carl

Yes I have not done the rear brakes yet, I am going to be doing that and dual rear calipers soon!