Originally Posted by cobalt327
There's a good chance that the booster- if sized for a disc/drum set up- is not large enough. For four wheel disc brakes you need a 7"-9" dual diaphragm or equivalent booster capable of 1200 psi. Usual vacuum required is 18 in/Hg although you might get by w/less, but pedal effort will increase as vacuum decreases. Vacuum reservoirs do not usually help very much; you can look into a vacuum pump if you have inadequate vacuum. But if this engine is basically stock it should be making enough vacuum.
You may need an adjustable proportioning valve, but other valves aren't really needed other than as a warning for system pressure loss, which can be plumbed separately.
From a post
You can do a search for more.
I have been doing research, and finding out more about the car as I go. Today I found out:
**The rear end of this car came from a 2004 Mustang GT, so it has the OEM brake calipers.
**The Front end has D52 style GM calipers
**The proportioning valve was a Disc/Drum valve that was modified (as you said It had the fitting/cap between the two front outlets) I was told buy a custom brake specialist to huck that thing into the nearest trashcan.
**I was also told by this custom brake specialist that my problem is more than likely due to the size of the Master cylinder bore which is 1 1/8" He explained to me, and it makes complete sense after thinking about it. I have more volume flowing to the calipers than pressure. Pressure is what I need. He is reccomending that I go to a smaller bore Master Cylinder which will in turn give me more pressure. Thinking back that would explain why it seamed the master cylinder would "bottom out" it was filling the calipers with a large volume of fluid but not enough pressure.
**He also thinks that the 7" dual diaphram booster is right on the edge of being maxed out. I estimated the vehicle weight at 3400lbs, I found a websight that listed a 56 crown victoria with the thunderbird v-8 at 3400lbs, so its got to be fairly close to that. He says the 7" dual boosters are good for about 3500lbs.
I ordered a new combination valve from them and should be getting it tomorrow. But after hearing what he was telling me and thinking it over I was thinking about the CPP MCPV-1 with a 1 inch bore. That way I would get the Master Cylinder I need It has a built in Proportioning valve, its a lot prettier than a Cast iron Corvette Master, Less line and clutter. The Proportioning Valve I ordered was almost 90 bucks shipped. The CPP master seams like a killer deal at 199.00, Big Pretty bang for the buck.
As far as the booster goes, I'm not sure I can go with anything bigger due to valve cover clearence. With the 7" I don't notice any resistance like it is struggling, I might just stick with that.
Any Idea, comments, insight?
Thanks in advance