Re: [AMC-List] Proportioning Valve

[<francis.swygert@xxxxxxxxxxxxxxxxxx>]

AMC used two pressure settings: 400 psi for Rebel/Matador/Ambo, 200 psi
for everyting else. So there was no fine tuning. The easiest thing to do
is get an adjustable proportioning valve and install it in the rear
brake line after the existing junction block. You can get them that have
pressure settings on them -- check various hot rod shops, Summit, and
Jegs. That would make it easy -- just set it to 400 psi. 

Alternately, get a GM combo valve. MP Brakes (www.mpbrakes.com)
recommends (and sells) that. It's used on all there hot rod and muscle
car installations. I don't know what psi it's set at, neither do they
for that matter. I suspect it's somewhere between 200 and 400 psi
though. It will take a little more plumbing work. 

Any valve from a big AMC will work, but note that in the 70s the big car
combo valve also had a metering function. That prevents the front brakes
from applying until ~100 psi is built up (a fraction of a second). It
takes ~100 psi to overcome the springs in drum brakes, so the metering
valve makes sure all four brakes apply at the same time. The drawback is
the plumbing -- two lines go fromt the master cylinder to the combo
valve with NO "T" to the right front caliper. The combo valve then has
three lines from it -- both front lines and a rear line. I don't know if
this setup was used through 78 or not, but as far as I've been able to
determine metering was never used on small cars. The late model (80s)
small car/Eagle comboi valve should work equally well -- it's a GM combo
valve. The small cars got heavier as time and safety regs progressed.
Check out XJ Cherokees as well. I've got an aluminum master cylinder and
combo valve (mounted very near the master) from one of those that I'd
intended to use, then decided to convert a Ford Ranger power brake
booster and master. 

With the adjustable valve you can get a short length of brake line (6"
is the shortest I've seen) and connect it directly to the junction
block. Then make an "S" bend in the original line and no lines will need
to be cut. Just make sure the "S" bend doesn't put the line to close to
the exhaust. 


----- original message --------
I'm trying to get started on changing over my Rebel to disc brakes from
drum. I have a complete front brake setup that I've had for yrs - all
well-worn, but all there. I had forgot what it came from, but from doing
some investigation, and comparing pictures of the calipers on
www.advanceautoparts.com, it looks to be the later ones that were used
on Eagles, some Jeeps, '82-3 Concords and Spirits. I was gonna test fit
everything together on the car, then exchange the calipers and rotors
for new/rebuilt. What I can't find is the proper proportioning valve for
this setup. Advance Auto has no listing. I'd think that any disc brake
car remote mounted valve would work. Anyone have ideas on where to find
one? I haven't explored the Napa site yet, or Autozone for that matter,
but thought I'd throw that out there. I'll probably keep it as manual
disc for now, just want it valved right; will sure be better than the
front drum setup I have on it now. 


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