Have a GM prop valve (disc front / drum rear). Since the brake pedal frame mounted, I got a 10psi residual valve for the rear and a 2psi valve for the front. On the prop valve, there are 2 ports for the front brake lines. Can I run the lines like this for the front? Plug one of the ports on the prop valve Run a short line with the 2lb residual valve in it. Then split the line with a T and run a line off the T to each caliper Will this effect braking? Should I just get another 2lb residual valve and run one on each line out of the prop valve? I'm not sure if only using one port will impact brake pressure and also not sure if a single 2lb pressure valve is good to hold back pressure on both front calipers.
Here you go, Dan. More good info on this site, if you need it. http://ecihotrodbrakes.com/images/pic02_brakefacts.gif
If you got rid of that fixed GM prop (probably a combo ) valve, you would need just one 2 lb residual to a front tee, one 10 lb to the rears, along with an adjustable prop valve. The result is a simpler and much better looking system, along with the ability to adjust pressure to the rear brakes for good balance. JMO.
The subject of proportioning valves has been thoroughly discussed in previous threads. The bottom line is, until you plumb and road test your brakes, you don't really know IF you will need a prop valve at all. It is the "conventinal wisdom" that anytime you have disc/drum brakes "you MUST have a prop valve". Just not so. Sometimes you do, sometimes you don't. It all depends on the specific "witches brew" of components, i.e. master cylinder bore, caliper piston size, rear wheel cylinder size, brake diameters and friction materials, tire sizes and weight distribution. I know that is not the question you asked but this answer is something you will find useful in sorting out your brakes even after you decide how to plumb the resdiual valve(s) for the front. If you check my posts from last year (early to mid 2010 I think) you will find a lengthy thread on this subect. Best wishes, Ray
"Conventional wisdom" is if you're going to include a prop valve, use one that can be adjusted, and not a fixed valve designed for one particular car, W/B, tire, GVW/LLVW weight, bias, etc. Fact is, most/all disc/drum and disc/disc non-ABS US vehicles did have a prop valve. (ABS systems perform this function without an external valve) If they wern't needed, the extra cost in parts, manufacturing and hours of brake balance testing would not have been spent. It's usually easier to plumb the PV in during the initial build vs having to add it later. You might not need a PV, but odds are you will.
Agreed...........in that it is easier to put in an adjustable one in the first place and go from there. Ray
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