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Posted by: Hammy Jul 29 2006, 02:58 PM

So this "quick" brake fix job has turned into another real headache. What's new?

Screwed up two of the rear brake hard lines when I was replacing the rubber lines. So we went down and bought some new metric hard lines at a FLAPS, they fit nicely, blah blah blah.

Now it appears that the threading for the right brake line IN the proportioning valve is stripped, and the brake line will screw into it but has a lot of play, is very loose and basically will for sure be leaking.

So now what do you think I should do? I've already spent so much on this brake fix job and I would *really* hate to spend 200 bucks on another P valve. The adjustable ones listed on PP say they're for track use only too. What about replacing with a T fitting? I've read of others doing that. Street car, stock brakes....

Thanks for any help...

Posted by: Aaron Cox Jul 29 2006, 03:12 PM

im sure someone has a stock one somewhere for free...

i threw mine away...

do a T if you have bigger than stock front brakes....

Posted by: Brad Roberts Jul 29 2006, 03:16 PM

You probably didnt buy the adapters you need for a prop valve.

None of the cheapo Summit or Wilwood prop valves will screw together with our lines.

Anyone figure out from this "why" I tell people to put a "T" in place?


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Posted by: Hammy Jul 29 2006, 03:20 PM

I didn't know there are adapters

Posted by: Aaron Cox Jul 29 2006, 03:21 PM

i think brad is talking about a wilwood p-valve that requires metric adapters

Posted by: Hammy Jul 29 2006, 03:22 PM

ah. gotcha.

Posted by: Brad Roberts Jul 29 2006, 03:24 PM

It's ok. I wasnt aiming that directly at you.

You dont need a prop valve.

One of the most common mistakes made is thinking that the 914 has a prop valve in it..when in fact it does not. It is just a "damper" it does not restrict flow to the rear calipers.

Honestly.. it only works in emergency situations, otherwise it passes fluid JUST LIKE A TEE.



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Posted by: john rogers Jul 29 2006, 03:30 PM

Put in a Tee, you'll be much happier!

Posted by: craig downs Jul 29 2006, 03:37 PM

From what I can remember they used to advertize it as some sort of anti lock device. They used to say you can push on the petal as had as you can and the brakes should not lock up.

Posted by: Hammy Jul 29 2006, 04:01 PM

Emergency situations meaning..... Sudden slam on the brakes in wet weather? Hard stop and they lock up... or??

Where can I find a T fitting? I'm thinking a bug shop?

Posted by: Aaron Cox Jul 29 2006, 04:02 PM

tee can be found at bug shop...

or CIP1.com, or james adams here on the baord

Posted by: Joe Ricard Jul 29 2006, 04:09 PM

I just went out and looked at the stripper.
nice shape factory Proprtioning valve. DAPO re did the entire system before dumping car.

Let me know I'll ship it Monday early. Make me an offer provide mailing address.

Posted by: Eric_Shea Jul 29 2006, 04:25 PM

I have T's in stock. $6 clams.

Me no likes taking the P-Valve out unless ness...

Posted by: James Adams Jul 29 2006, 04:49 PM

The stock valve is a proportioning valve (pressure regulatiing valve). Here is the factory pressure curve.


Attached image(s)

Posted by: Brad Roberts Jul 29 2006, 04:59 PM

Correct.

In a panic situation. The graph shows the relatively high pressure it takes before it slows down the fluid to the rear calipers.

Porsche calls this a "damper'


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Posted by: James Adams Jul 29 2006, 05:15 PM

Porsche calls this a "Brake Pressure Regulator" and the curve looks the same as the Wilwood, Tilton, and Kelsey Hayes valves, as that is what they are.

It may also be called a damper by Porsche somewhere, but this does not mean it is no longer a proportionaing valve, which it is.

Posted by: Brad Roberts Jul 29 2006, 05:23 PM

Looks the same when?

When the Wilwood and others are wide open?

Every single time I have installed an adjustable brake bias valve (Wilwood etc) Every time.... I have had to run them wide open. At that point, why run one in a stock system?

Posted by: James Adams Jul 29 2006, 05:47 PM

The stock valve knee point occurs at about 680 psi. This is equivalent to position 4 (out of 7) on a lever type Tilton valve, or about midway on a rotary Tilton, Wilwood, or Kelsey Hayes.

Now, whether the stock valve is set appropriately is another debate, but saying that putting a tee in is the SAME as a stock valve is not a legal situation I would want to place myself in. A rising limit starting at less than 700 psi is definitely effective, and is not well above what you may reach in threshold braking.

The 914 may welll brake better with the valve gone, just as dialing out understeer in most production cars will make them corner faster, but it is not something you just lay out there for the uneducated.