hi ed,
in the mustang system, gutting the OE prop valve also eliminates the
front/rear loss of pressure safety system. i.e. if you get a cut brake line
you lose only half your brakes, not all your brakes. any modification like
this needs to retain this important safety feature.
i hope the SS system is not like this!
-james
----- Original Message -----
From: "Runnion, Ed" <Ed_Runnion@RegionOfDoom.com>
To: <ba-autox@autox.team.net>
Sent: Thursday, January 16, 2003 9:25 AM
Subject: Adj Proportioning Valve
> >I'm just curious, because I ended up pulling my adjustable prop valve
> >out of the Firebird because I couldn't get enough pressure to the rear.
> >There has been discussion of gutting the OE prop valve, THEN adding an
> >adjustable valve in the rear line...
>
> If it is the same/similar to the Impala one, this should work.
>
> The Impala SS, stock (4-wheel disc), has proportioning of 97%F/3%R (no,
that
> is NOT a misprint!). These numbers have been measured on a brake plate
> tester by Hunter BTW, and are repeatable on many (stock) cars. This is
> because GM used the same proportioning valve as on the disc/drum
> Caprice......man, I LOVE those beancounters :^).
>
> A very common mod (it's been done on thousands of the cars in the Impala
SS
> enthusiast community now) is to "gut" the valve (basically remove a
plunger
> and spring) and replace the front bolt with an aftermarket one that is not
> vented.
>
> After the "bolt" mod, the brake bias is a much better 70%F/30%R.
> Car brakes more confidently, easier to modulate, less brake dive, and the
> rear brakes are actually DOING something :^).
>
> I know this type of mod is done in the Mustang world as well, and I
believe
> it can be done to an F-body also.
>
> An "adjustable" proportioning valve should really be called a brake
> "limiting" valve. In other words, it can only "limit" line pressure, not
> increase it. So if your car has too little rear brake bias, putting the
> valve on the rear line will make the problem worse.
>
> Hope this helps!
>
> Ed Runnion Ed_Runnion@RegionOfDoom.com
> 96 Impala SS, enjoys embarrassing many smaller "sporty" cars in braking
> tests
> 02 Subaru WRX Wagon, getting further from "stock" every day
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