installing an adjustable prop valve in the brakes

I need to install an adjustable prop valve in the rear to keep it from locking up on hard stops.i have a 14 bolt with discs in the rear.ive done this before on other vehicles but ive always installed them in the rear by the diff.the problem ive encountered is that they got cruded up with mud and everything else and basically became unadjustable in short time.i would like to keep it under the hood in the eng compartment but how would I route it to get it up there?it still has to go thru the stock prop valve too right?

Two prop valves is a bad idea. Remove the stock one, put the aftermarket in its place.

What front brakes are you running? Even with a wilwood adjustable valve, i could never get the bias right on my 44/60 setup.

its a dana 60 front with 3/4 ton calipers and a 14 bolt rear with the same 3/4 ton caliper setup.all works fine but in a sudden or panic stop on the street the rears lock up.i would like to adjust just the amount going to the rear after the main prop valve.

Then you want a brake limiting valve. Keep the stock prop valve and install one AFTER the stock part going to the rear brakes. They're small, you can mount it under the hood.

yes that's what I ment to say.i want it mounted under the hood.is there a writeup here?

Talyn said:

Two prop valves is a bad idea. Remove the stock one, put the aftermarket in its place.

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+1. Under hood for this is just fine.

XJLI said:

Then you want a brake limiting valve. Keep the stock prop valve and install one AFTER the stock part going to the rear brakes.

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Bad idea, you never want two of these in series. Now if you disconnect and plug the ports for the rear you can run the second in parallel, but's that something different all together.

I'm curious : why do you want to run two valves?
Why not just run a single manually adjustable valve under hood?

You need to remove the stock block. Grab a double flarin tool. Run the fronts straight up with a T. Plumb the wilwood prop valve into the rear line. You will making some new lines and using new fitings. Adjust the new valve in steps. Ive installed wilwood valves into 2 different rigs.

ive done this on my sons Toyota(the write-ups said as long as its after the main valve its ok)and ive also done it on my 86 montecarlo to reduce the braking in the rear.

markg said:

ive done this on my sons Toyota(the write-ups said as long as its after the main valve its ok)and ive also done it on my 86 montecarlo to reduce the braking in the rear.

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Who's write-up? No one who works on / designs brakes systems would say that's OK. You effectively end up with unpredictable results on what the rear brakes are doing any give time given the interactions of the two devices.

How about a white paper from guys who do design serious brake systems?
http://stoptech.com/technical-support/technical-white-papers/proportioning-valves

"We’ll start here with three of the most basic rules regarding proportioning valve installation and selection.
1. If you have the deeply-rooted need to install your own adjustable proportioning valve, be advised that they should NEVER be installed if the factory unit is still in place. Proportioning valves in series with one another can do nasty, unpredictable things!
2. If you have the deeply-rooted need to install your own adjustable proportioning valve, be advised that they should NEVER be installed in-line to the front brakes. The effect would be to make your vehicle rear-biased before you could say “terminal oversteer.” Front brake line pressure should always be left alone – only the rear pressures should be considered for proportioning.
3. In all cases, the basic brake system balance needs to be close to optimized to start with. This is the only way that a proportioning valve can be effectively utilized. You should never assume that simply adding a proportioning valve will address all rear-bias conditions, as even the best proportioning valves must be well-matched to the target vehicle."

im sorry maybe im wording this wrong. I do appreciate all of your help and advice and I know if done wrong this could be very bad.is it possible that I am referring to the stock prop valve as the distribution block?this is not my setup its just something I found on the net but it is the master cyl im using.doesnt it seem here that they are using the stock dist block and just adding a manually adj prop valve on only the rear? are you saying I can eliminate everything by just tying the fronts together and putting the manual valve going to the one line going to the rear?

http://image.chevyhiperformance.com...07ch_03_z+1969_chevrolet_nova+brake_setup.jpg

The distribution block you linked the picture of typically contains internal valving to control pressure to the rear brakes and most folks call the whole thing the prop or proportioning valve. The front brakes should just be a pass through in that block. The rear brake lines should have a spring and internal valving between the input and output ports. What you want to avoid is having two valves in series (one after the other).

Options:

You can eliminate the distribution block entirely by connecting the front lines presently running in/out of the distribution block together with a coupler, and the rear in and out lines are joined with an adjustable aftermarket prop valve. (Note the distribution block can be used as a coupler if desired, but the rear lines won't be hooked up to it. That's what I was trying to allude to by referencing plumbing the two devices in parallel).

You can also gut the internals of the distribution block so the rear valving doesn't do anything (effect now both front and rears are just pass throughs) and then add the adjustable unit downstream. I hoping that's what Chevy High Performance did, but it certainly looks sketchy in the picture you posted.

Removing the internals also combine both brake circuits. Not a good idea.

Talyn said:

Removing the internals also combine both brake circuits. Not a good idea.

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That's just weird that they'd design it that way, but point taken and certainly something to look for.

Most manifolds are machined from solid so you should be able to see what's going on and what you'd gut (or not guy) when you take it apart. Drills and taps don't go around corners so it's almost always exclusive plunge cuts.

Junkyard couplers are easy enough to find that there's really not many good reason to keep the former prop valve/distribution block around anyways.

I tried it that a while ago. Braking was horrible. When you remove the internals there is nothing but an empty cavity between the front and rear systems.

I replaced the combo valve on mine a while ago, using a union for the front brake system. I posted this in another thread:

Talyn said:

I put a manual prop valve in mine. I went with a Wilwood prop valve, 260-10922 with 3/8-24 flare fittings. I used the following adapters from Royal Brass (mine has ABS so it may be a bit different).

Brake prop valve adapters:
2x BQ260 - 1/2-20 female thread w/ 3/16" tube to 3/8-24 male thread
1x 240CB - 7/16-24 female (w/ 3/16" tube) to 3/8-24 (w/ 3/16" tube) male thread
1x 42IFHD-3 - 3/8-24 union (w/ 3/16" tube)

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Here is also another option: http://www.naxja.org/forum/showthread.php?t=1114077