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If you call Wilwood they will tell you to use there adjustable valve in the line going to the rear brakes.

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On a race car with big slicks on the rear and skinnies
on the front.... I wouldnt put the adjustable valve
on the rears... front yes... reason why... a adjustable
prop valve is nothing more than a delay, all the pressures
will equalize after a period of time depending on
how the valve is set, so with skinnies up front and
you put the valve in the rear you are slowing the fluid
to the rears and giving full fluid to the front giving
the front all/most of the load on the tires... they
just arent big enough to carry that load
If this was a street car with equal size tires then
yes I would put it on the rears to slow the tires
from locking up as the frontend dives on braking
and the rear gets light

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Pbody,in your opinion with a car with 3.5 wheels up front and 10 in tires out back would you use one or not?

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Yes I would... I'd put it on the front lines to slow
the fronts from locking up under hard braking. The
prop valve is nothing more than a adjustable orifice
and the more you close the valve(less braking on the
initial hit) but after a short period of time the pressure
will equalize (dependent how its set)

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If you call Wilwood they will tell you to use there adjustable valve in the line going to the rear brakes.

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On a race car with big slicks on the rear and skinnies
on the front.... I wouldnt put the adjustable valve
on the rears... front yes... reason why... a adjustable
prop valve is nothing more than a delay, all the pressures
will equalize after a period of time depending on
how the valve is set, so with skinnies up front and
you put the valve in the rear you are slowing the fluid
to the rears and giving full fluid to the front giving
the front all/most of the load on the tires... they
just arent big enough to carry that load
If this was a street car with equal size tires then
yes I would put it on the rears to slow the tires
from locking up as the frontend dives on braking
and the rear gets light

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It was brought up once before but I don't recall what was said:

Does a typical Mopar master cylinder have a certain amount of natural "proportion" built into it? In other words, would there be any difference in front-to-rear pressure without a proportioning valve......and would swapping the lines at the MC change it front-to-rear, if needed?

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I have seen some that did have different prop in the
master but from what I was told the 60/40 is the
volume difference in the reservoir... unknow for fact

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It was brought up once before but I don't recall what was said:

Does a typical Mopar master cylinder have a certain amount of natural "proportion" built into it? In other words, would there be any difference in front-to-rear pressure without a proportioning valve......and would swapping the lines at the MC change it front-to-rear, if needed?

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A quick test while bench bleeding would be, once you
get it bled put the 2 lines(that you have going back
into the res) bend them over so you can have them
squirt into 2 measuring beakers... if its a different
volume its a build in prop valve

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The proportioning in most mopar style master cylinders are a rated volume usually aprox,65%fr-35%r.This is volume only,not pressure.They were set this way for the disc/drum combos since large single piston or daul 4 piston calipers required more fluid volume than the small brake shoe wheel cylinder. Most race proportional valves are adjustable from 0 to 1000psi. most common manual brake systems working range is 400 to 600psi.

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Right in the mopar parts catalog when they are describing the MC % they are saying volume or displacement, not pressure.

Think about this. On a mopar MC the front port usually goes to the rear brakes. The only way to have 2 different piston or bore sizes would be for the front piston to be smaller which would generate a higher pressure to the rear brakes. So that would negate your theory, I think.

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Ok i only slept 3 and ahalf hour last night.
But im really working my brain here trying to figure out how a smaller piston can give you higher pressure.

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Right in the mopar parts catalog when they are describing the MC % they are saying volume or displacement, not pressure.

Think about this. On a mopar MC the front port usually goes to the rear brakes. The only way to have 2 different piston or bore sizes would be for the front piston to be smaller which would generate a higher pressure to the rear brakes. So that would negate your theory, I think.

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There are two pistons of the same diameter on a common rod moving the same distance. They move the same amount of fluid per stroke and have the same pressure potential. It doesn't matter if the front of the reservoir or master cylinder bore holds five gallons and the rear only holds six ounces. They both move the same distance.

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The master cylinder volume is to displace the area of the of the pistons or wheel cylinders.A proportioning valve controls the pressure.A stock valve and a race valve do the same thing they open and close the passing orfice which controls the pressure,ie: putting your finger on a garden hose to increase the pressure.Small race calipers with small pucks can use a small MC(less area,less volume)large street calipers with large or multiple pucks need larger MC bores and resovires. By adjusting the size of the passing orfice(making it smaller) increases the pressure,usually in to increase and out to decrease on the race valves

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The master cylinder volume is to displace the area of the of the pistons or wheel cylinders.A proportioning valve controls the pressure.A stock valve and a race valve do the same thing they open and close the passing orfice which controls the pressure,ie: putting your finger on a garden hose to increase the pressure.Small race calipers with small pucks can use a small MC(less area,less volume)large street calipers with large or multiple pucks need larger MC bores and resovires. By adjusting the size of the passing orfice(making it smaller) increases the pressure,usually in to increase and out to decrease on the race valves

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So you sre saying that a propvalve is nothing more than a finger on the hose.
Dont get me wrong here i want to learn this but wouldnt the finger keep the caliper pistons from returning and drag the rotors?
Or is it a spring actuated valve of somekind?

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It is like putting your finger over the hose BUT
with the brakes its going into a closed area(line
and caliper) SO the pressure will equalize on both
sides of the valve after a giving period of time.
All that valve is is a delay on the pressure... in
hyd, the pressure will equalize

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So without a prop valve you will have the same pressure at all 4 corners? the same stopping power at all 4 corners?

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Yes if the pistons in the master are the same, the
only difference would be the size of the caliper
pistons or wheel cylinder sizes... but if the master
pistons are the same you have the same PRESSURE

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Not necessarily the same stoping power. I have the same calipers at all 4 wheels but my front rotors are 10-1/2" and the rear rotors are 12+" so the rear will have more stopping power. Gee maybe that is why I don't have the need for a porportioning valve since I run big&little tires...........

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Very true, the farther you get from the centerline
the easier it is to stop the same mass

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With that being said would it be harder to do a burnout without a prop valve?

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With that being said would it be harder to do a burnout without a prop valve?

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You just have to hold the brake pedal a little longer
for the pressure to get to the fronts(remember it
will equalize)... most people including myself pump
the pedal a few times and hold it then press the line lock

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With that being said would it be harder to do a burnout without a prop valve?

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You just have to hold the brake pedal a little longer
for the pressure to get to the fronts(remember it
will equalize

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huh

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With that being said would it be harder to do a burnout without a prop valve?

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You just have to hold the brake pedal a little longer
for the pressure to get to the fronts(remember it
will equalize

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huh

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Tony.... if you have a prop valve in the fronts the
pressure will be SLOW getting past the prop, then
it will equalize after X period of time

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The master cylinder volume is to displace the area of the of the pistons or wheel cylinders.A proportioning valve controls the pressure.A stock valve and a race valve do the same thing they open and close the passing orfice which controls the pressure,ie: putting your finger on a garden hose to increase the pressure.Small race calipers with small pucks can use a small MC(less area,less volume)large street calipers with large or multiple pucks need larger MC bores and resovires. By adjusting the size of the passing orfice(making it smaller) increases the pressure,usually in to increase and out to decrease on the race valves

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So you sre saying that a propvalve is nothing more than a finger on the hose.
Dont get me wrong here i want to learn this but wouldnt the finger keep the caliper pistons from returning and drag the rotors?
Or is it a spring actuated valve of somekind?

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Your not comprehending this at all,the pressure is only when the piston is depressed in the master cylinder which inturn pushes the fluid through the system pushing the pucks and applying the brakes,when the pedal is released so is the pressure,simply theory of hydraulics pressure applied through the pedal ratio,applied through mc bore/stroke,controlling a given volume at a given pressure.Change in pressure can be regulated by the size of orfice it passes through.The small orfice holds back the volume(under pressure) and the orfice creates the additional pressure.ie: a nozzle on a fire hose or pressure washer.Sorry I can't explain it any simpler,hope it helps you understand.Another example would be a diesal fuel injection system where as a pump generally pumps fuel at 45psi to the injector nozzle the nozzle orfice releases fuel at 1800psi.