I've been running front discs (mid-80's Chevy C-10 style) with rear drums and a Chevy firewall-mounted S-10 disc/drum style master cylinder/booster/distribution block setup with a Wilwood adjustable proportioning valve plumbed into the rear. I've installed rear discs from a mid-90's Crown Vic now, and I'm not sure what to do with regards to the M/C and distribution/proportioning setup. And I'm not even sure how to tell if what I think is a distribution block actually has some kind of prop valve built into it. What do I do next?
I'd be tempted to try plumbing the Wilwood valve in a standard "rear" throttling setup. Then see if they are locking up too early.
Well , I've never done it before but, If I was in your shoes I would look at buying a m/c from a S-10 Extreme . I'm almost positive they had rear disc brakes & proportioning valve from a 90's Crown Vic w/disc brakes. That's what I might do.
The accepted method for disc-braking a fox mustang is to "gut" the spring and piston from the stock prop valve and plug the rubber end. This disables the proportioning, which won't work for four wheel discs. Then tweak your adjustable valve on the rear brake line so you don't loop it.
Impala SS/ Taxi Cop car M/C is what I put on my S-10 when I went four wheel discs. But then again, it had Impala spindles with LS-1 brakes all the way around.
"The accepted method for disc-braking a fox mustang is to "gut" the spring and piston from the stock prop valve and plug the rubber end. This disables the proportioning, which won't work for four wheel discs. Then tweak your adjustable valve on the rear brake line so you don't loop it. " This is a GM valve (or block) but I'm thinking I could see if there is a valve in the rear circuit outlet, and remove it if there is one. What is this "Rubber end"? Nothing like that on mine. "mc for disk/disk will be needed. " Do I for sure need a different M/C? I've read a couple of guys saying that they have used the S-10 master with 4 wheel discs successfully.
I've not fiddled with a GM setup so my apologies if this is all nonsense, but it might be similar. On the fox prop/combo valve there is a plug in the forward end of the block that has some manner of rubbery cone running through it. Unscrewing that displays the valve, spring, and seal. Remove those and chunk. Replace with a solid plug with o-ring to seal the end. I have no idea what the rubber cone thing is for, but this conversion worked well for me. http://www.jalopyjournal.com/forum/showpost.php?p=3550931&postcount=7 you can just see the valve body and plug at the bottom of the first pic in this post. J
If you've driven the vehicle, you've probably noticed the brake pedal traveling further than normal. You're sending a lot more fluid to the rear now, so you need to go up on m/c bore to compensate. You will probably need something with a 1 1/16" bore or 1 1/8" bore. Find out what bore you have upsize. Does the distribution block have anything other than tubes in and tubes out?? The prop valves I'm familiar with usually have an extra capped or plugged port where the spring and valve are installed.
I was wondering the same stuff when setting up my brakes for my F100. I stumbled on this- really simple, but really well- explained: http://auto.howstuffworks.com/auto-parts/brakes/brake-types/master-brake2.htm http://auto.howstuffworks.com/auto-parts/brakes/brake-types/brake.htm http://auto.howstuffworks.com/auto-parts/brakes/brake-types/master-brake.htm
I forgot I had a pic of my setup. Here it is: I see it does have a cap of some sort on the end. So if I'm understanding it is: 1. Gut the copper block above of any valving (I'll still have the adjustable valve just downstream), then refill, bleed and try it out. If the pedal feel is bad then: 2. Replace the master with one with a bigger bore. Right?
I decided to gut the combination valve. I took off the little rubber boot at the front of the combination valve and removed the metering valve & spring assembly as seen in this diagram: Do I: 1. Just need to JB Weld the hole in the cap and re-install, or does something else have to be put in place of the pieces I just removed to keep the "Switch piston" from blocking the brake fluid at the front inlet? or... 2. Could I skip the JB Weld and just clip the spring so the proportioning feature would be disabled, and let the diaphragm and metering valve seals do their regular job and seal it up?
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